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Abstract

Investigation of animal-related crime, and therefore submission of forensic cases to veterinary pathology facilities, is increasing, yet many veterinary pathologists are unfamiliar and often uncomfortable with involvement in the forensic necropsy. This article discusses various aspects of the forensic necropsy without specific attention to any particular species group or crime. General advice is given on procedures, documentation, and recording of the examination, and the article indicates how these features may differ from those used in investigation of natural disease. It also discusses evidence management, including recordkeeping, identification of evidence, labeling of photographs, and use of standard operating procedures and protocols. Various written and visual methods for documentation of the forensic necropsy are covered, and adjunctive topics such as sample collection, assessment, and description of wounds and taphonomy are included. Cause, mechanism, and manner of death are defined, and guidance to the use of these terms is given. The aim of this article is to offer guidance on procedural aspects of the forensic necropsy that will help those developing their forensic services, contribute to standardization of the provision of forensic veterinary pathology, and build the confidence of the “uncomfortable” forensic veterinary pathologist.

Keywords

forensic veterinary pathology necropsy standard operating procedures protocols postmortem examination quality control

Forensic veterinary necropsies have a broad range of indications, including neglect, nonaccidental injuries, unlawful killing, animal abuse, infringement of wildlife laws, transportation violations or other environmental investigations, theft, human protection, malpractice or disciplinary procedures, and insurance claims.* Evidence garnered in animal-related crimes is often directly pertinent to the investigation or understanding of interpersonal violence or of human-centered crime.^{1,4,5,7,58,59,71,75,76} This review concentrates on medicolegal forms of investigation (ie, where a crime is suspected of having been committed) and does not aim to include malpractice or insurance procedures (although certain aspects may be relevant to these types of investigation). The diversity of reasons for submission has the potential to impose multiple approaches to the necropsy, as do the various weapons or modes of animal abuse that may be involved. Adding to this complexity is the breadth of the species range encompassed by forensic veterinary investigations. This review therefore concentrates on generic issues of procedure pertinent to forensic necropsies, although some specifics will be included as appropriate.

The Role of the Veterinary Pathologist in Forensic Veterinary Investigations

The veterinary pathologist is required to act in an independent, objective, and unbiased manner in forensic investigations. The role of the pathologist is not to pass judgment but to document, interpret, and explain the pathological findings to the investigators and ultimately to the court, thereby assisting the court to reach a decision on the case. The pathologist must also help the court to understand the significance (or otherwise) of pathological changes associated with natural disease, common injuries, or incidental, perhaps age-related, findings.^53,61 Conclusions stated by the pathologist should be based on facts or informed opinion. To fulfill these roles with competence and confidence, those conducting forensic necropsies should have training and, ideally, experience in diagnostic veterinary pathology. As is the case with any professional or expert witness to the legal system, the forensic veterinary pathologist should stay within the boundaries of their competence and experience unless able easily to access suitable expertise in, for instance, less familiar species, weaponry, or analyses.^20,60 Currently, the term forensic veterinary pathologist is used to denote trained and certified veterinary pathologists who have additional forensic qualifications or who have documented, relevant experience in forensic practice.

It is not intended in this review to describe in detail how to conduct a necropsy since trained veterinary pathologists will be well versed in conducting systematic examinations and in recording them—usually on a designated postmortem report form—in a similarly structured manner. These skills are applicable to both forensic and diagnostic necropsies. That there are differences between a diagnostic necropsy and one performed as part of a medicolegal investigation should, however, be highlighted.^36,52 In the latter, as well as a thorough documentation of all natural and acquired (inflicted) pathological changes, specific questions may form part of the initial instruction or may be explored during the subsequent court case.^20,36,66

The forensic veterinary pathologist may be asked to confirm whether suspected inflicted injuries can be confirmed as such and how the injury may have been caused. Is the injury consistent with an alleged incident or with the account of the accused? Can it be confirmed that the injuries were sustained antemortem? If so, for how long might the animal have survived after the injury and, often the crux of a case, was suffering involved? The pathologist may be asked to estimate the time between death and discovery of the body. Did the animal drown or was he or she already dead when thrown into water? Is there evidence to suggest burial when still alive? Did the animal die in the fire? Is it possible to estimate the duration of deprivation of food or water? In investigations involving wildlife species, there may be additional questions relating to sex or reproductive status.²⁰ The pathologist may be asked whether the findings of the necropsy are specific or whether there might be an alternative cause.

Questions such as these may seem daunting to veterinary pathologists, but it should be reiterated that the pathological evidence forms part of the whole investigation, and it is the responsibility of others to piece together all forms of evidence from the investigation and to pass judgment. To play their part in this process, the forensic veterinary pathologist must be careful, thorough, and systematic, using an approach that ideally is informed by experience and training, but also to remain open-minded. In support of this are the procedures and protocols surrounding the forensic necropsy, which underpin the legitimacy of the evidence.

Before the Necropsy

It has been discussed previously whether forensic veterinary pathologists should perform necropsies “blind,” that is, without prior knowledge of the case,^54,63 and that even if a history is provided, it may be incomplete or unreliable.²⁰ The amount and quality of history accompanying each case will vary, but at the very least, the forensic veterinary pathologist should be aware what specific question(s) investigators have with regard to the examination.^20,36,63 Veterinary pathologists should explore with those instructing them whether there are aspects of especial relevance requiring attention, and it is a good idea to include the requirement to address these specific aspects in the introduction to their report.⁶³

It is less common for forensic veterinary pathologists to attend the “scene of crime” (or locus) than it is for forensic medical examiners. If possible, however, attendance at the scene is helpful to understand the circumstances of discovery and possibly the recent history of the animal. Signs such as soiling of the hair or feathers, marks and wounds suggesting struggling or restraint, or extraneous material associated with the body (soil, vegetation, soiled bedding) may be better understood with a visit to the scene. Knowledge of the practical aspects of retrieval of a particular body will help the pathologist put into context skin wounds that may have been caused by moving or dragging a body from a scene. Similarly, patterns of livor mortis or postmortem shifting of fluid or bruising, which may occur when a body is moved from the position in which it died or was placed soon after death, may be better understood with such information. Alternatively, a veterinarian, preferably one with interest and experience of forensic cases, may have attended the scene, especially when live animals are present,^54,67,69 and may be able to provide useful intelligence. Reports (including visual representation—video, photography) from the scene of discovery may be obtained from humane society officers, police officers, or wildlife investigators. It should be made known to the veterinary pathologist whether the animal was still alive when seized and thus received veterinary attention before dying or being euthanized and, in the case of the latter, the manner of euthanasia. All such information is highly valuable to the forensic veterinary pathologist in interpretation of necropsy findings.

Evidence Management

Evidence management and, within this subject, the maintenance of continuity of evidence (“chain of custody”) are discussed in other articles in this special edition, so only a few aspects appertaining to forensic necropsies will be discussed herein. Depending on the case and the circumstances of retrieval, the cadaver may be considered an item of evidence or to be a crime scene in its own right with all associated material (biological or otherwise) as evidence relating to the “scene.” Either way, it should be borne in mind that, as with other forms of material evidence, the contribution of the necropsy evidence to the case relies on there being demonstrably no compromise, contamination, alteration, or substitution of the evidence, or any part, during the entire process of the pathological examination—from arrival at the pathology facility to presentation in court and/or to handing over of the remains to another party or disposal at the facility. Thus, as with other parts of an investigation, the whole process requires secure custodianship of the evidence with procedures to ensure appropriate handling and storage and auditable recording and inventory protocols. Pertinent ancillary tests should be performed by competent providers (with recognized quality assurance accreditation and relevant sample handling protocols), and release of material from the pathology facility for these tests should be fully documented. Within this aspect of evidence management, ensuring that continuity of evidence is demonstrable throughout becomes an interesting challenge, and the specifics of these processes may vary slightly between facilities and even with different types of animal or investigation. However it is achieved, being able to demonstrate robust evidence management can certainly boost the confidence of the veterinary pathologists who finds themselves called to attend the court hearing.

Some aspects of evidence management to consider are discussed in the succeeding paragraphs.

Case Folder

Maintain a securely filed folder for the case containing hard copies of significant paperwork such as the cadaver receipt, signed and dated by the person delivering the body and by the recipient; a record of unique identifiers, such as evidence, incident or case number, and the original labeling of the specimen (thus documenting a link between these and the laboratory accession number, which will have been assigned to the case upon receipt); and a “significant event” log recording actions such as the day/date/time the bag was opened, when imaging was performed, when the necropsy started, who was present/involved, when the examination was temporarily stopped and when it resumed, when the examination was concluded, and when and to where the remains were moved for storage. Each significant event entry should be signed and dated.

Evidence Identification

Take care that cadavers and parts removed are identified, usually by use of permanent indelible and ideally freezer-proof labels (various types are available) throughout the examination. It is especially important to label the remains at key stages in the examination. After full reflection of the skin, for instance, the carcass denuded of any external markings becomes anonymous. Secure attachment of a label in a position that it will not be removed or interfere with subsequent dissection, such as the tail base or the pelvic girdle, ensures continuity of identification.

Secure Storage

Material to be retained at the conclusion of the necropsy should be stored securely, ideally sealed in clearly and uniquely labeled bags in secure refrigerators or freezers. Samples separated from the parent cadaver should also be labeled carefully and retained securely and their movements tracked. For instance, parts of a carcass may need to be stored separately or taken out of storage to be radiographed in isolation or to be shown to another expert. Similarly, all other material removed from or found with the carcass, such as paint flakes, ballistic evidence, bedding, pieces of plastic from the stomach, and even toys, towels, collars, and leads, should be carefully gathered, labeled and stored appropriately, or passed on to an appropriate agent. A record of where all materials and items have been stored, how they were labeled, when they were deposited or handed over, and when and how they were disposed of could be made in the significant events log in the hard copy folder. A separate inventory of refrigerator/freezer contents is a valuable way to keep check of what remains have been retained and where.

Cadavers from forensic cases should ideally not be stored in open-access refrigerators or freezers. Material or cadavers should also not be left unattended; if there is an intermission in the examination, for instance, the remains should be moved to a secure place for the duration of the interval, and this should be recorded.

Labeling of Photographs

Labels should be included in all photographs (see “Photography” below) and a complete copy of the photographs retained securely.

Protocols and Standard Operating Procedures

Protocols for certain repeated necropsy procedures can be devised. For instance, a standardized technique for removal and examination of the respiratory tract of animals found at the scene of a fire can be drawn up.⁶⁵

Written standard operating protocols for all the above and additional procedures, drawn up and used at the facility, can be appended to necropsy reports and statements, with cross-reference within the text of the reports. In this way, the procedures followed do not have to be written out within the statement pertaining to each case, and a consistent approach can be maintained.

These types of measures give the investigators and the court a clear statement as to how the evidence was managed and how individual procedures were undertaken. If such protocols are drawn up, however, it is important to regularly review them, especially in the early stages of their use, to ensure they are relevant, workable, and—importantly—followed.

Documenting the Examination

Contemporaneous Notes and the Necropsy Report

Contemporaneous notes (or audio recordings) made at the time of the examination are part of the pathologist’s investigation. Investigators may request submission of the original (blood-splashed) written notes or recording of a necropsy as an appendix to the final typed report of the case. In this event, written notes could be provided, sealed in clear document sleeves for hygiene purposes. If health and policy reasons do not allow paper notes to be removed from the necropsy room, then the originals may be photographed, photocopied, or scanned (as facilities allow) and the copies signed and dated as such by the pathologist(s).

The necropsy report, which must be typed up from the contemporaneous notes as soon as possible after the examination, should follow a structured systematic format, as would a diagnostic necropsy report. It should be borne in mind that cases may not proceed to a court hearing for several months, maybe a year or more, after the necropsy has taken place, and it is easy to forget the details of a particular animal, so descriptions should be clear and comprehensive and all organs or tissues examined should be noted, even if just to say that there were no significant gross abnormalities. If a structure was not found or was omitted from the examination, this should also be recorded.

The pathologist’s report must aid understanding by the largely “lay” members of the court, and it can be a challenge to pathologists who have spent their residencies learning how to write “correct” pathological descriptions to write reports devoid of anatomical or pathological jargon for the courts. Use of “familiar” terms (windpipe, belly, broken jaw) alongside the specific anatomical or pathological terms will help the courts, as will a summary of the most significant findings and their implications in laymen’s terms appended to the technical pathology report. Comments of significance or opinion should be accompanied by references where possible to demonstrate that the remarks are based on current state of knowledge. When compiling a postmortem report, it is important that the pathologist is mindful that the necropsy findings are a record of the facts of the case (ie, the evidence), while the conclusions/opinion form a separate section based on interpretation of these findings and other relevant evidence.

Many investigators and courts will be familiar with the terminology employed for physical injury since they are used in medical forensic investigations, so it is important that such terms are used correctly and appropriately. Commonly used terms for traumatic wounds and their application in veterinary necropsies are discussed in general terms in the following paragraphs. More specific and detailed discussion of injury types is included in other articles within this special issue of the journal, and various medical and veterinary forensic texts give fuller details.^{29
–31,48,55,56,60,64,87}

Abrasions

An abrasion is a superficial wound to the skin often involving a tangential force. The defect may subsequently be covered by serum and cellular crust, possibly with entrapped foreign material, or, if extending into superficial dermis, there may be mild hemorrhage at the site. In human pathology texts, it is noted that with tangential abrasions, rough tags of epidermis may remain at the terminal margin of the defect and may helpfully indicate direction of the blow. In veterinary species, with the cushioning effect of the hair or feather coat, this feature may not always be apparent.

Note also that postmortem abrasion of the skin as a result of movement of the body is not infrequent; an example of this is often seen over the bony prominences of the skull when large animal bodies have been dragged using a winch.

Contusion and Bruising

These are terms used for escape of blood from the circulation into encircling tissues and are often used interchangeably, although strictly speaking, bruising occurs deep to an intact dermis while contusions are collections of escaped blood anywhere in the body, such as in parenchymal organs such as the spleen. Bruising is subject to comprehensive discussion in human pathology texts, especially the different patterns of bruising caused by various instruments or trauma. In most hirsute veterinary subjects, for the most part, bruises are difficult to detect without full reflection of the skin. In forensic necropsies, this is best achieved by interconnecting skin incisions made along the ventral midline from chin to pubis, along the medial aspect of each limb and encircling each distal limb, with gradual undermining of fascial attachments to allow separation of the skin in 1 piece (ideally).⁶⁰ Once this is done, the pelt can be stretched out underside uppermost and this, as well as the naked torso, examined and photographed to demonstrate more clearly any bruising (or other wounds). In view of the fact that many veterinary species are skinned routinely in the abattoir, a number of informative surveys of subcutaneous bruising in farmed species have been undertaken with a view to identifying traumatic stages in the meat or cull industries and to reducing production losses.^6,92,93 Shape and type of weapon used may give similar bruise patterns in animals as in human subjects, but again hair or feather cover should be considered. In addition, while many are aware that extravasated blood changes color with time in the live animal, it should be borne in mind that bruises will, to varying extent, alter in distribution after death. There may be gravitational pooling of leaked blood around the ventral neck from a skull injury, for instance, or radial seepage along tissue interfaces from a focal bruise, so the veterinary pathologist should be circumspect in interpretation of causes of bruises. Finally, medical forensic pathologists, especially those investigating child abuse cases, need to be aware of overinterpretation of bruises that have an innocent cause,⁵⁰ and the same applies in veterinary species. Examples include bruising over the hip of a cow caused by regularly impacting a door frame when entering the milking parlor or the rough “play fights” of young dogs. Obtaining as much information as possible from the background of the animal is of value to aid interpretation.

Lacerations

These are full-thickness breaches of the skin that are caused by blunt trauma, as opposed to incision by sharp object (see “Incised Wounds” below). Lacerations generally require a firm base and minimal subjacent soft tissue in order for complete penetration of the skin to occur, and again there may be a cushioning effect of the hair or feather coat. Thus, lacerations tend to occur with forceful impact over bony prominences, such as hammer blows to the skull. Many lacerations may appear at first inspection to be incisions, although careful examination of a wound may reveal that in the case of a laceration, hair or feathers at the wound’s edge have not been cleanly transected, and there may be ragged tissue strands, nerves, and blood vessels crossing the skin defect (tissue bridging).⁸⁵ Because of the associated crushing force, bruising is usually also a feature of lacerated wounds.

The relatively slender abdominal wall offers little protection from blunt-force injury to abdominal organs, and sudden rotation of viscera at their point of suspension or traumatic splitting within skeletal muscles may be caused by the transferred energy of the impact. In these cases, tearing and shearing are often prominent, and somewhat confusingly, laceration is also used to describe such internal injuries.

Incised Wounds

These are wounds inflicted by sharp instruments, and this category encompasses slashes or cuts—where the resultant defect is generally longer than it is deep—and stab wounds or penetrations—where the offending weapon is inserted to a depth greater than the length of the wound. Chopping wounds may also be described, and in these, where a heavy weapon such as a hatchet may have been used, there may be an element of tissue laceration as well as incision.^30,48 Hairs or feathers at the wound margins are likely to be sliced cleanly, as are the skin edges, and bruising may be less pronounced, although depending on the tract of a stab, internal hemorrhage may be considerable.

Wound Assessment

It was indicated above that the shape of the skin defect or the damage to underlying tissues may convey information about the weapon used. In experimental work that assesses wounding pattern achieved with various weapons, animal tissues or anesthetized animals are frequently used as models.^† It should be remembered, however, that unless the first blow renders the animal unconscious or immobile, an attack is a dynamic situation. Shapes of injuries are affected by the relative postures and stances of assailant and animal victim, variations in skin tension, the angles of thrust and withdrawal of a sharp weapon, and the force of each blow of a blunt instrument. Thus, the veterinary pathologist should be cautious about overinterpreting wound shapes and of using them to definitively describe potential weapons.

In medical forensic medicine, it is noted that “popular” weapons are often dictated by local legal restrictions—for instance, in countries with rigid gun laws, knives are more often carried and therefore used in interpersonal attacks,³³ and in domestic settings, the knives are likely to be those readily available in the kitchen or among the hobbyist’s accoutrements (including craft or hunting equipment). In street settings such as among gangs, certain weapons can attain status, for instance, serrated survival knives.¹⁸ Blunt weapons used in spontaneous attacks may include what was on hand at the time such as screwdrivers and hammers.^23,94 Veterinary pathologists may find it helpful to be aware of trends in weaponry noted in medical forensic medicine. As yet, there is inadequate information to confirm similar trends in attacks on animals, but it is likely that these patterns of weapon use may be reflected in veterinary cases.

Taphonomy and Postmortem Alterations

A number of contributing factors will leave their mark on the remains, including autolysis, decomposition, predation, submersion, and attempts to conceal or dispose of a body.^{3,19,27,38,81,96,97,100} Experimental work suggests that decomposition rates vary between species⁹¹ and, at least in human bodies, between individuals.³⁴ The retrieval processes, time intervals before storage, and mode of storage of the body (eg, freezing) prior to the necropsy will affect the state of the body and influence the examination process. The forensic veterinary pathologist should still proceed with attention to detail and conduct and report on the examination within the limitations imposed by the state of preservation of the remains. Experiments with animal tissues suggest that even in poorly preserved remains, imaging or dissection may reveal fracture patterns¹⁹ or ballistic information,² discriminating toxicology may be possible,⁹⁹ or informative extraneous material associated with the carcass may be retrievable.^24,72

Nevertheless, in the case of poorly preserved remains, there is a need to explain to investigators the limitations of the necropsy and to exercise caution with interpretation of findings.

Photography

A full set of photographs should accompany the pathology report. Photography should start before the necropsy—before unwrapping of the carcass if it arrives in packaging. As soon as the case receives its own unique identifying (accession) number, a label for use in the photographs can be generated, which includes this identifier, and this must be included in every picture. An overall photograph is taken of the bagged carcass, or large animal, followed by a closeup photograph of any labeling with which the animal arrived. Bags are often sealed with a numbered cable tie, and large animals may be submitted with a label tied to a limb; the closeup photograph of these unique labels will now be captured along with the accession number of the pathology facility. A photograph of any paperwork submitted with the carcass at this stage is also of value. Thereafter, if the body is wrapped in more than one layer of covering, photographs should be taken at each stage of the unwrapping process. Before starting the necropsy, the external appearance of the animal is photographed from as many different angles as appropriate to the animal’s size to obtain a comprehensive view of the whole animal. Any other unique features—ear tags, tattoos, brands—should also be captured at this stage.

Thereafter, the examination should be recorded by repeated photography throughout, although avoid quick “snaps”; take a similar level of care when photographing findings as would be used for a publication. All findings, including incidental or nonsignificant changes, should be recorded, and where appropriate, it may be helpful to include “negative” findings—where tissues can be demonstrated to have no gross significant abnormalities. Care should be taken with framing of the photograph. Place the identity label near to the area of interest and stand back to take an overall orientation view. Then, without moving the label, take a closeup view of the particular finding, ensuring that it is as central in the view-finder as possible and that the label is also included.

Try to keep the photographs clean and uncluttered. Provided that material or fluids that may have evidential value are not lost in the process, clean an area to be photographed. Paper or card arrows, colored wires, or probes to indicate a particular feature are helpful, but avoid inclusion of extraneous dissection instruments or gloved hands. Similarly, if possible, try to avoid lakes of blood, spilled gut contents, or autolysis fluid (unless they are pertinent to the photograph). It is important that the photographs are clear and understandable to the court—albeit with the guiding interpretive comments of the pathologist—and that they convey an air of methodical and thorough examination and not a haphazard and messy dissection.

Photographs should be taken in a continuous numbered series. A complete set of photographs should then be stored securely and traceably, whatever form is used, and this complete set needs to be available to investigators or the court without any alterations or deletions—even photographs that are out of focus or inadvertent irrelevant shots should be retained in the master set. Many cameras record the date and time on the image, and it should be ensured that settings are accurate before starting to take photographs. An index of the photographs taken, with a brief indication of the subject of the photograph or the reason for taking it, should be drawn up using a clear serial number for each photograph. For instance, the index may be a printed set of the photographs with their number and a brief caption, or it may be a tabulated list with a comments column. It is permissible then to take copies (or scans) of photographs from the master copy to illustrate the pathology report or statement and to subsequently amend these copy photographs as required, such as by adding labels to structures or inserting arrows to clarify a finding. These copies must be saved or labeled as copies and not included in the master set.

Imaging Techniques

Imaging techniques (according to the facilities) are invaluable in forensic necropsies.^{11,15,41,42,83,95} Most practically, they can be performed before dissection while the cadaver is still sealed within its wrappings, which ensures cleanliness and hygiene in clinical facilities, but is also good from the point of view of evidence management. The value of imaging in gunshot injury has been discussed by others.^67,73,74 This may reveal information about the weapon used, the position of retained missiles, fragments or gunshot residues within or under the skin, and the tracts caused by the shot or dislodged bone fragments. Imaging is also of value in cases of suspected raptor poisonings where, for instance, the bird has eaten the poison-baited carcass of a shot rabbit—the shotgun pellets may then be viewed within the crop or stomach.⁶⁷ Lead residues from missiles may be observed radiographically and radio-opaque residues are retained and visible even in an extensively charred body, such as might be the case when an attempt has been made to dispose of the carcass by burning.² Even without externally apparent wounds, imaging can be informative,¹¹ especially in veterinary species where detection of bruising or wounds can sometimes be challenging on external examination. Bone fractures and dislocations are identifiable in situ, before artifactual misalignment of bone fragments caused by dissection. Imaging can also overcome the masking of bone injury by surrounding hemorrhage and soft tissue damage. Similarly, signs of bone reparative processes, suggesting serial beatings or neglect of an injury, may be visible and can be indicated to the courts. Radiographic views demonstrating loss of bone density may help demonstrate chronicity of undernutrition.⁶² Closure of growth plates may have evidential importance when confirming the identity of immature animals or during the investigation of bones recovered from graves containing more than one animal. Finally, imaging techniques have been employed experimentally in animal models, in the estimation of time since death.^9,41,42

With modern digital imaging techniques of whatever kind, the images can be securely stored locally or by use of a central storage facility and can be retrieved and viewed at a later date, even after disposal of the cadaver.¹¹ Postprocessing techniques are investigator independent and objective and accessible for audit.⁸² A copy of the images can be submitted via portable data storage or central files can be accessed, and in court, the images can be viewed as hard copies or via a computer connected to a large screen. For the courtroom, imaging is a more accessible and acceptable visual representation of physical wounds in an animal than the sometimes gory photographs from the necropsy hall. The 3-dimensional reconstructions from computed tomography (CT) are especially clear and understandable to lay observers and can be rotated on the computer screen to give a graphic view of areas of interest and angles of an attack.

Sample Collection and Ancillary Testing

Procedures vary from one facility to the next over the collection of specimens at necropsy for further testing. Immediate ancillary tests may be undertaken, or it may be considered prudent to archive a range of samples (with appropriate evidence management protocols) pending further lines of inquiry in the investigation, which may suggest the need for particular tests at a later date.²¹ Thus, samples may be collected for toxicology, chemistry, microbiology, histopathology, DNA identification, or entomology. (More information on collection of trace materials and for biologic materials on the body is included elsewhere within this special issue of the journal, such as in the discussion of sexual abuse of animals.)

Depending on the case, the pathologist needs to give consideration to the benefit to be gained from undertaking specific laboratory tests to complement the findings of the gross necropsy. Tissue samples from a range of organs are routinely collected into fixative by many pathologists, but there is no imperative to process all or any of these samples unless the results of histopathology are likely to advance, materially, the interpretation of the initial necropsy, especially where the body is poorly preserved. As discussed in detail by Munro and Munro,⁶⁶ histology may be useful as a guide to the age and timing of wounds with reference to established progression of tissue healing,^25,37 although it should be remembered that data for all our animal species are not yet available, and extrapolation between species on exact timings is unsound.^35,36,66,90 For this reason, published tables of histological features and timings or ages of wounds should be considered guides and not absolutes, and each case will be subject to unique individual and environment-specific factors. Newer immunohistochemical, genetic, or other microscopy techniques have been developed, and some have been successfully applied to experimental animal models to assess various wound types,^26,46,47 but validation and routine use in most veterinary species remain distant.

Aspects relating to estimation of time since death are also discussed comprehensively in Munro and Munro,⁶⁶ and studies have been conducted in a limited number of animal species using various techniques.^{32,45,80,81,84} In general terms, collection of samples for toxicology, biochemistry, or entomology might be vital to the determination of the cause of death or establishment of an approximate time of death, and having protocols and the necessary sample containers for these specialized procedures is essential.²¹ If such ancillary testing is undertaken, the results must be included and interpreted in the final postmortem report even if the results appear to undermine the necropsy findings.

Cause, Mechanism, and Manner of Death

In medical pathology, determination of the cause, mechanism, and manner of death is required. DiMaio and DiMaio²⁸ define the cause of death as any injury, disease, or disorder that initiates the physiological derangement (morbid events) leading directly to the death of the individual; examples in forensic pathology would be stab wounds or blunt force to the head. If an unequivocal cause of death is not recognized at autopsy, then the report must contain the statement that cause of death is “undetermined.”³⁶ The more specific the cause of death that is recorded, the more informative will be the report to the courts. It is worth noting that in veterinary investigations, euthanasia is not the initiating event of disease or injury and, as such, should not be recorded as the cause of death.

The mechanism of death is the physiological derangement so caused. Note that one mechanism may be produced by a number of causes; for instance, fatal hemorrhage may result from a stab wound or from blunt force to the abdomen sufficient to rupture the liver. More than one mechanism of death may follow one cause—the blunt-force injury to the skull could cause cerebral edema or penetration of the brain by implanted bone fragments. So far, these terms are as applicable to the forensic veterinary as to the forensic medical investigation.

The manner of death is somewhat different. This is a summary statement of the circumstances under which the cause of death occurred and is essentially the opinion of the medical examiner based on the facts known about the case in conjunction with the autopsy findings. There are 5 conventional categories into which the death will be placed: natural, homicide, suicide, accident, or undetermined, and the information is collated for various epidemiological uses. As noted by Gerdin and McDonough,³⁶ this classification is not suitable for forensic veterinary pathology, not least because the terms used are not all appropriate to animals. Manner of death in veterinary investigations can be described as natural or unnatural, and the latter category may be subdivided (eg, injury, chemical, or undetermined). However, forensic veterinary pathologists should be cautious about requests to provide a manner of death merely because the courts may expect one, and this caution should be elucidated.

Conclusions

There is much to be learned in the field of forensic veterinary pathology. We must be cautious about extrapolating directly from medical pathology texts or even from animal models used for advancement of human forensic pathology when the animals used may not represent all veterinary species⁶⁶ or the conditions of the experiments are such that the results may not be representative of findings in the “field.”^12,101 Suggested approaches to the forensic necropsy are already available in specific texts on the subject,^20,36,54,63 and with moves to propagate information between practitioners in the field,⁵² it is anticipated that there will be rapid growth in forensic veterinary pathology as a discipline in its own right and not merely by extrapolation from forensic medical pathology. Nevertheless, building supportive multidisciplinary networks of experts, including medical pathologists and other forensic scientists, is clearly beneficial.^4,13,22,54

Necropsy findings can be immensely important because they provide documented observation of injury, natural disease, neglect, and decomposition. These observations may provide unique insights into events occurring both before and after death. Nevertheless, each case has the potential to introduce some novel or unexpected feature and should be viewed as a learning opportunity. Consequently, it is useful to keep notes on how an investigation went, then to review procedures or report-writing technique as experience is gained. Above all, thoroughness in the conduct of each case is the key to the delivery of sound advice that assists the court.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Notes

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The Veterinary Forensic Necropsy

Abstract

Keywords

The Role of the Veterinary Pathologist in Forensic Veterinary Investigations

Before the Necropsy

Evidence Management

Case Folder

Evidence Identification

Secure Storage

Labeling of Photographs

Protocols and Standard Operating Procedures

Documenting the Examination

Contemporaneous Notes and the Necropsy Report

Abrasions

Contusion and Bruising

Lacerations

Incised Wounds

Wound Assessment

Taphonomy and Postmortem Alterations

Photography

Imaging Techniques

Sample Collection and Ancillary Testing

Cause, Mechanism, and Manner of Death

Conclusions

Footnotes

Declaration of Conflicting Interests

Funding

Notes

References