Evidentiary Rigour of a DNA Match

Abstract

DNA evidence has been used in India in criminal and civil matters since 1989. Despite the use of DNA fingerprinting evidence in trials, it is not ‘generally accepted’ by Courts, as against the technique of fingerprinting, which has been used for decades as incriminating evidence. Further, its acceptability as forensic evidence in Indian courts has been challenged, citing relevance and reliability. The current article provides a review of the conventional principles of evidence admissibility in courts and its pertinence related to DNA evidence in India in the backdrop of civil and criminal case laws of the country.

Introduction

DNA profiling is a technique used to chemical divide the DNA complex into fragments that form a unique pattern and then to match that identity profile with the pattern obtained by similarly testing a suspect’s blood specimen. ¹ DNA profiling, as a forensic test, was first put to use by Sir Alec Jeffreys in 1985 in the case of a maternity dispute. ² It was first applied to a criminal investigation in 1986 in England after two girls, aged about 15 years, were found raped and strangulated near the village of Narborough. ³ It arguably has been the most dramatic advancement that has ever occurred in the field, but its acceptance, especially in the Courts, has not been without challenges. ⁴ Though DNA evidence has met the challenges in some countries through scientific reasoning and legal scrutiny, it happens to be in a struggling phase in India. Science has no borders for its acceptability; however, the novel scientific evidence must meet the standards of legal acceptability according to the constitutional and legislative provisions of different jurisdictions. This article attempts to clear the issues regarding the current status of the admissibility of ‘DNA evidence’ in India.

Background: Acceptability of New Scientific Evidence

Scientific evidence is accepted by courts only if it stands the scrutiny of legal tests set by case laws. These legal tests or guidelines for scientific evidence have not been adequately explored or discussed in Indian courts for DNA evidence. A review of such legal tests is discussed, followed by their applicability in Indian courts as regards DNA evidence.

Legal Tests and Cases

The admissibility of scientific evidence has evolved through the legal challenges of accepting it. The acceptance of evidence depends on its relevance and reliability. Various tests that apply before evidence is admissible are as follows:

Frye’s test (‘general acceptance’ test): Frye mandates that a novel technique must pass through an experimental stage in which the scientific community scrutinises it. Only after the technique has been tested successfully in this stage and has passed into the demonstrable stage, it will receive judicial acceptance. It means that expert scientific evidence should not be deemed admissible unless and until the methods and principles on which it was based have achieved widespread acceptance in the relevant discipline. Thus, through this statement, Frye had delegated the burden of evaluating complex scientific merits, from judges to the scientists who are the experts in their particular discipline. It was argued that Frye’s standard is only a proper condition for taking judicial notice of scientific facts and not a suitable criterion for the admissibility of scientific evidence, and relevant conclusions supported by a qualified expert witness should be received for its admissibility. Frye’s test was accepted in the landmark judgement of People v. Castro ⁵ and Kunhiraman v. Manoj. ⁶

Daubert’s guidelines: In Dauberts’s case, the court held that an expert’s scientific testimony must establish a standard of evidentiary reliability, and in order to admit evidence as scientific, it must be both relevant and reliable. The factors can be summarised as follows ⁷ :

Whether the theory or technique can be or has been tested (its falsifiability, refutability or testability);

Whether the theory or technique has been subjected to peer review and publication;

The known or potential error rate of a technique;

Whether the theory or technique has received ‘general acceptance’.

Novel evidence must go through the rigour of Daubert before it is admissible. Exclusions owing to procedural errors are usually beyond the control of the expert witness. Reliability factors relating to the exclusion of expert witness testimony may include failure to address reliability in the context of the case, use of unfounded statistics, failure to adhere to recognised standards, insufficient documentation of analysis, inability to clearly explain the methodology, custom experiments, lack of objective standards, the existence of observer bias, unrealistic proficiency testing and the insufficient relationship of expertise to facts of the case. ⁸

Doheny case: Landmark guidelines have been laid down in 1996 when judgement was given in the Doheny case. ⁹ Several relevant points from this judgement can be summarised as follows ¹⁰ :

The scientist should properly explain to the jury the nature of the match between the stain found at the crime scene and the suspect.

The scientist should give the frequency of occurrence with which a matching DNA profile is likely to be found in the population.

It might be appropriate if the scientist has the necessary data and statistical expertise to say how many people might be found to have matching profiles in the relevant section of the population.

The jury would then decide, on all the information available, whether the stain originated from the suspect or some other individual with a matching DNA profile.

Bayes’ theorem: Analysis by Bayes’ theorem shows how the probability of a false positive could influence a proposition that a particular individual is the source of a biological specimen. It takes into consideration both scientific and non-scientific pieces of evidence. In the case of DNA evidence, the likelihood of a DNA match is affected by both the probability of a random match and the probability of a false positive. If we consider the traditional standard of proof in criminal cases, that is, the crime must be proved ‘beyond a reasonable doubt’ and the dictum that ‘it is better that ninety-nine offenders should escape than that one innocent man should be condemned’, then the posterior odds ratio must exceed 99:1. When the random match probability is of the order of 1 in one billion (10⁻⁹), then it can meet this threshold. Such random match probabilities are possible when laboratories are able to match two single source samples over 10 or shorter tandem repeat (STR) loci, which is now a common norm. ¹¹

False positive results may occur while processing DNA matches. They may occur due to mislabelling, mixing the wrong ingredients or failing to follow routine precautions against contamination. Although the probability of such a false positive may be between 1 in 100 (0.01) and 1 in 1,000 (0.001), its impact on the strength of DNA evidence does not decrease if other pieces of evidences are fairly strong to implicate the accused. However, in cases where other pieces of evidence against the suspect are less, ignorance of the true probability of error creates a disturbing element of uncertainty about the value of DNA evidence.

However, courts may have different views on ‘random match probability’ and ‘Bayes theorem’. As regards ‘random match probability’, ¹² it is held that the statistical interpretation of DNA evidence is undeniably strong evidence pointing to a conclusion that the accused was the source of the incriminating DNA but is not the direct evidence of that fact. However, when DNA evidence is analysed in the light of non-DNA evidence by Bayes theorem, ¹³ it is likely to be rejected as it involves subjectively attaching numerical values to evidence and usurps the role of the jury. Thus, the court laid down a proper approach in this case by saying that the judge must treat the statistical evidence along with the other circumstantial evidence, not allowing it to displace or overwhelm the consideration of all material evidence. Similarly, if there is any evidence like an alibi, which suggests the absence of the accused while the crime was committed, it cannot be overtaken by DNA statistical evidence.

Legal Fallacy

While arguing the question of the probability of a match/no match of the DNA evidence in a court, one has to take into account two fallacies: the prosecutor’s fallacy and the defendant’s fallacy.

These can be dealt with by the following two questions:

If we assume that the accused is innocent, what is the probability of his DNA sample matching with the one recovered from the scene of the crime?

If we assume that the DNA profile of the accused matches with the one recovered from the scene, what is the probability that he is innocent?

This was explained by the US Supreme Court in MC Daniel v. Brown, 588 US 120 (2010) ¹⁴ :

If we consider that the frequency of a DNA profile match is 1in 10,000 and that the suspect’s DNA profile matched with the one from the crime scene, the prosecutor may erroneously express that there is only a 1 in 10,000 chance that the suspect is innocent. (Prosecutor fallacy)

However, taking the same argument further, if the population of the city is 1,00,000, then there are at least 10 individuals in that city alone who would possess the same DNA profile as the suspect. The defence may argue that just in the city alone, there are at least 9 more people who could have committed the crime. (Defendant’s fallacy)

Medical Predicament

It is a known fact that monozygotic twins have 100% similar DNA profiles. Theoretically, there are conditions wherein the DNA of two individuals may match. It has been observed that the individuals who had undergone successful bone marrow transplants show a true mixed profile of recipient and donor (in buccal and fingernail samples) or purely a donor’s profile (in the blood), with the exception of hair, wherein the recipient’s profile remains unmixed. Similarly, stem cell transplants may raise the risk of identical DNA, and such possibilities may have serious implications in civil and criminal law. ¹⁵

Indian Scenario

The admissibility of DNA evidence in Indian courts can now be discussed considering the guidelines and various standards for accepting novel scientific evidence. Tables 1 and 2 summarise some of the seminal cases in India, both civil disputes and criminal cases. The first case where DNA evidence was accepted in India dates back to 1989 and 1991 when it was used in a paternity case.^{6, 12, 15, 16} ‘General acceptance’ by the scientific community was sought in its initial proceedings. Similarly, population statistics were used in an argument to prove the admissibility. ⁶ Since then, the DNA results are being given due recognition by Indian courts, and in most cases, it is accepted that if the DNA result does not match, then the identity of the person is not established and vice versa. ¹⁵

Table 1.

Criminal Cases that Scrutinised DNA Evidence.

Sr. No.	Case	DNA Evidence Accepted/Rejected	Reason	Court
1.	MV Mahesh v. The State of Karnataka 17	Rejected	No prima facia case to order a DNA test, where the evidence adduced was enough to reach a conclusion. Quantity that was required for the test was not sufficient Bones did not belong to Beena The method followed by the expert was not universally adopted.	Karnataka High Court (1995)
2.	Swami Shradhananda Case 31	Accepted	It was the first in which the DNA analysis of the skeleton remains of an exhumed body was used as evidence in a court of law.	Supreme Court (2008)
3.	Beant Singh Assassination Case	Accepted	Helped in nabbing the main accused/suspected in the human bomb blast.	Punjab and Haryana High Court (2012)
4.	Naina Sahni (Tandoor Case) 32	Accepted	Helped in establishing the identity of the victim.	Supreme Court (2013)
5.	Rajiv Gandhi Assassination Case 33	Accepted	Not only helped in identifying the victims but also helped in establishing the identity of the accused by extracting the DNA from the flesh attached to the belt.	Supreme Court (2000)
6.	Priyadarshini Mattoo Case 15	Rejected by ASJ (1999) Accepted by Delhi High Court (2006)	Rejected: Tampered with swabs, slides and accused samples Samples reduced when opened at lab Delay in the submission of samples in Malkhawna The accused was given the benefit of the doubt. Accepted: There was no fault in the DNA testing DNA was recovered from the sperm stains present over the swabs, slides and underwear.	Supreme Court (2010)

Table 2.

Civil Cases that Scrutinised DNA Evidence.

Sr. No.	Case	DNA Evidence Accepted/Rejected	Reason	Court
1.	Kunhiraman v. Manoj Case 6	Accepted	Manoj had inherited a total of 15 bands, which were not derived from the mother, but derived from the Kunhiraman alone; therefore, it was proved beyond doubt that the Kunhiraman is the biological father of Manoj.	Kerala High Court (1991)
2.	Gautam Kundu v. State of West Bengal 34	Rejected	Supreme Court made the following guidelines: The courts in India cannot order blood tests as a matter of course. No one can be compelled to give blood samples. It was not a violation of the right to personal liberty under Article 21. Matrimonial courts have the power to order a person to undergo the test.	Supreme Court (1993)
3.	Rohit Shekhar v. ND Tiwari Case 35	Accepted	A single-judge bench of the High Court ordered the DNA analysis, but ND Tiwari refused to give blood samples and applied against the order, but the double-judge bench of the High Court upheld the single-bench order. The Supreme Court also refused the stay order.	Delhi High Court (2012)
4.	Banarsi Das v. Teeku Dutta 36	Rejected	DNA Tests cannot be directed as a matter of routine and can be conducted only in deserving cases. The case in discussion does not fall into that category.	Supreme Court (2005)
5.	Nandlal Wasudev Badwaik v. Lata Nandal Badwaik 37	Accepted	Court held that ‘when the conflict between a conclusive proof envisaged under the law and a proof based on scientific advancement accepted by the world community to be correct, the latter must prevail over the former’.	Supreme Court (2014)

In the case of MV Mahesh v. The State of Karnataka ¹⁷ and Priyadarshini Mattoo, ¹⁸ reliability factors not related to expert witnesses resulted in the rejection of the DNA evidence. The rigour of DNA evidence was tested by Daubert’s guidelines without directly referring to them. It is apparent that in such cases while the court takes judicial notice of scientific evidence, conclusions are drawn by balancing the probative value of the evidence against the danger of unfair prejudice, confusion of issues or misleading the jury.

Population statistics for ‘random match probability’ has been a contentious issue and has recently been raised in the Arushi murder case by a London-based genomic expert. ¹⁹ It was highlighted that DNA evidence submitted by the prosecution was not powered by ‘random match probability’, that is, the lack of data regarding the frequency of alleles in the population. Doheny’s case also highlighted the same contentious issue. Of late, population statistics of allele frequency are available through various studies from West Bengal, ²⁰ Andhra Pradesh, ²¹ Karnataka, ²² Arunachal Pradesh, ²³ Madhya Pradesh, ²⁴ and other subsets.^{25, 26} These studies showed that there was genetic polymorphism to such an extent that these databases can be used for forensic identification. However, this argument remains unexplored by the Indian courts. The probable reason may be that DNA profiling complexities are perceived untenable and incomprehensible by defence counsel so as to explore its fallacy or that the frequency statistics may be beyond 10⁻⁹ (achieved by analysing 10 STRs). Indian laboratories are analysing 16 STR loci, the product rule frequency of which may exceed the world population. Nevertheless, even though DNA profiling achieves exceedingly high levels of individualisation, it does not theoretically indicate uniqueness.

Another lagging area is the inappropriateness of DNA technology. In the world scenario, the Technical Working Group on DNA Analysis Methods (TWGDAM, 1988), National Research Council I (1992), National Research Council II (1996) and Scientific Working Group on DNA Analysis Methods (SWGDAM, 1999) were formed to address the general applicability and appropriateness of DNA technology to forensic science. They also acted as a forum to discuss issues, conduct studies and reach a consensus on the DNA methodologies to use. ²⁷ It was stated that due to these working groups, now there remains no problem that could prevent the full use of DNA evidence in any court. ²⁸ However, the use of DNA profiling as established evidence is still in the budding stage, and the government is struggling to legislate the ‘DNA Technology (Use and Application) Regulation Bill, 2019’ which purportedly intends to introduce the use of DNA for forensic and other purposes, provides guidelines for the appropriateness of DNA technology, administration and licensing of DNA laboratories and also seeks to create DNA database. ²⁹ However, till it sees the light of day, the reliability and relevance of DNA evidence depend on legal ‘acceptance’ by the Apex Court.

By reviewing the seminal cases from India, a summary of the admissibility of DNA profiling evidence can be as follows:

The DNA technique and its scientific validity have received a judicial notice and have not been found to be disputable. It is accepted as such. As evidence, it withstood the standard of admissibility as mandated by Section 45 of the Indian Evidence Act, of 1872. ³⁰ Expert scientific evidence is covered by Section 45, in which the relevance of an expert’s opinion is closely connected with competency. Therefore, courts were considering the competency of the expert as a criterion for admissibility rather than the reliability of the scientific theory or technique he used for arriving at a conclusion.

Its admissibility as per Daubert’s guidelines was considered, but each of its principles was not tested in every case.

Population statistics and random match probability were discussed in a few cases. However, courts did not refute the evidence even if such statistics were not up to the mark. Effects of other errors like false positives on the evidence reliability seemed to be unexplored.

The evidentiary value of DNA profiling was refuted only on grounds of sample handling and strength of the chain of custody thereto.

Courts have considered DNA evidence in corroboration with other non-DNA evidence in cases that may have varying cogency. A review of judgements shows that isolated DNA evidence was not presented by the prosecution to incriminate the accused.

DNA evidence was used for incriminating the accused and also for excluding the innocent.

DNA evidence was given priority over Section 112 of IEA related to the paternity dispute.

Many cases have relied upon ‘general acceptance’ or ‘acceptance by the courts’ as reasoning for the admissibility of forensic evidence. However, it is reasonable to comment that ‘acceptance by the courts’ does not qualify as ‘general acceptance’ under Daubert.