Evidence in the genes

Print edition : January 02, 2004

The problems and prospects of DNA fingerprinting.

THE Government of India has just announced the setting up of a committee of experts to study the issue of a new comprehensive legislation to govern DNA (deoxyribonucleic acid) testing for criminal investigation. This welcome move has not come a day too soon. Apart from experts in a broad spectrum of disciplines, the committee will also include a few police officers. This is appropriate because law enforcement agencies in the country, especially the Central Bureau of Investigation, are now more than convinced that DNA fingerprinting is an effective and generally reliable tool that can add value to investigation and bring quick results.

Forensic experts at a scene of robbery and murder in Bangalore.-G.P. SAMPATH KUMAR

The CBI employed this technique in the sensational Madhumita Shukla case of Uttar Pradesh. Trying to establish a motive for the murder of the young poetess, the CBI is said to have established through DNA testing that Madhumita carried, at the time of her death, a foetus whose DNA matched with that of Amarmani. The theory is that the horrific deed was committed in order to silence her when she became persistent in her demand that Amarmani marry her. These are media speculations and whether these will be confirmed ultimately in court is beside the point. What is relevant here is that a premier agency such as the CBI has chosen to take advantage of the facility available. This is a milestone that will inspire State police forces as well. I am sure that many of them are already employing the technique to solve some of their difficult cases.

DNA testing should be viewed against the fact that the growing citizen concern over crime is not merely about mounting statistics. It is also over the detectives' inability to solve many gruesome crimes. The question that is often asked of me is how far the police are equipped to handle investigations using modern science and technology, and how far does the current law of evidence in the country recognise evidence gathered from such tests. I always detect more than a trace of popular cynicism over police willingness to spurn third degree methods in favour of scientific investigation.

It is mainly in this context that the issue of DNA profiling is raised frequently by many critics of police performance. Some human rights activists may also raise the basic question whether it will be appropriate to subject a suspect or a convict to such testing. In my view, however, the former should rather be pleased with the prospect that techniques such as DNA testing could persuade policemen to abjure barbaric third degree practices.

DNA fingerprinting helps law enforcement agencies or courts to determine an individual's involvement in a crime, settle a dispute over paternity or to process applications for immigration. It was developed by Sir Alec Jeffreys, a professor at the University of Leicester in the United Kingdom in 1984. This was sequel to his discovering that certain sequences were repeated within a gene that do not contribute to the function of a gene.

While the DNA's chemical structure is the same for all of us, there is a recognisable difference in the order in which the millions of base pairs found in each person's DNA is arranged. It is this differential that is captured by DNA testing. Since mind-boggling numbers are involved here, scientists focus on repeating patterns in a sample and on a small number of sequences that are known to vary greatly between individuals. The exercise undertaken by the expert here is one of comparing two samples and decide whether they are from the same person or from those related to each other.

The remarkable feature of DNA is that individuals leave at least traces of it almost everywhere. A few of the everyday objects handled by us, such as pens, telephones, mugs and keys are some of the things that require attention from a crime investigator. A variety of offences such as murder, rape, armed robbery, extortion and drug trafficking yield themselves to the application of DNA collection and testing. According to a study by the National Institute of Justice (NIJ) of the United States' Justice Department, there are many unusual sources of DNA evidence that need to be explored by an investigator. These include saliva found on the flap of an envelope containing a threat letter, spittle collected from the sidewalk where a suspect in a sexual assault case was under surveillance and blood collected from a bullet that had injured an assailant himself in a case of murder.

NIJ Journal

There are several fundamental issues that need resolution before DNA testing becomes a valuable and acceptable aid to crime investigators. These include the twin problems of making the test reliable, consistent, and therefore acceptable to courts, and the building of a national database that is comprehensive enough for an exhaustive search. Each of these bristles with difficulties, some solvable and some not.

A few researchers are skeptical about the finality and accuracy of the test results. They posit it against the kind of proof that criminal courts demand of the prosecution. According to them, DNA testing suggests at best a very high probability and not a conclusive proof that a person whose sample had been tested was in fact involved in the transaction under investigation.

THE unwitting contamination of samples is one of several circumstances under which courts have sometimes rejected DNA evidence. Courts are known also to ask for proof that the test is free from subjectivity of interpretation of data. A few others have turned down DNA evidence on finding that the laboratories had not conducted all the tests that they were required to perform. One difficulty that is often highlighted here is that of the laboratories getting stuck with samples collected from the scene of crime and sent to them by the investigator for a thorough analysis.

Not only is the quantity available to them is limited for the purpose of performing all the tests called for. There is additionally the possibility of the degradation of samples over time. Also, there is the risk of the undetected mixing of samples of several individuals (as in the case of multiple murders) in the sample provided to laboratories. These are the haunting features of all tests conducted in laboratories much after the crime. This factor has made courts extremely circumspect while considering DNA evidence.

Interestingly, a 1923 U.S. Supreme Court observation in Frye vs U.S. still influences judicial thinking in a few countries. The court said: ". ... while courts will go a long way in admitting expert testimony deduced from a well-recognised scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the field to which it belongs." The current position in the U.S. itself is that the rigid standards set by this pronouncement are not always followed by courts in that country to admit or turn down DNA evidence. The general feeling, however, is that Frye will definitely come into the reckoning where a court finds a division of opinion within the scientific community. I must cite here a strange happening in 1989 during The People vs Castro hearing before the New York Supreme Court. Here Castro was accused of the murder of a neighbour and her daughter. The bloodstain found on Castro's wristwatch was sent for DNA examination. The scientists who examined the sample concluded that "the DNA patterns on the watch and the mother matched, and ... the frequency of the pattern (was) about 1 in 100,000,000 in the Hispanic population".

However, the scientists on the prosecution and defence sides were for some reason uneasy about the test result and worried whether the finding was likely to mislead the court. Therefore, they took the unusual step of going into a lengthy conference to explore the gray areas in the Lifecodes system of DNA profiling adopted by the scientists in the case. Finally, they issued a consensus statement to the effect that the DNA data provided to the court in the case were not reliable. This was a startling admission that one could not blindly accept a DNA test report. The belief now is that courts will be willing more often to use the findings of a test to exclude a person from criminal liability than to include him. This position derives some strength from the fact that several prisoners on the death row in the U.S. have been released from prison in the past few years on the basis of post-conviction DNA tests.

All these issues will definitely crop up when India legislates specifically to give statutory recognition to the tests. Until then, the present Indian Evidence Act will prevail and DNA test findings will continue to be presented as expert evidence.

A second major obstacle to the widespread use of DNA testing is the non-availability of a comprehensive database and the enormous backlog of cases in laboratories. The latter is a more immediate problem. Convinced that this is an efficient tool, many investigators are increasingly resorting to it. As a result, work is piling up in many laboratories, especially in the U.S.

According to an NIJ estimate, about 350,000 rape and homicide cases are pending for DNA testing in the U.S. In March, Attorney-General John Ashcroft allotted $1 billion for nationwide strengthening of laboratories. DNA testing is an expensive process and there are only a few Indian laboratories equipped to do this. This places limitation on the building up of a national database that would store the DNA profile of many convicts. A strong database is one way of tackling the many cases where investigation is stuck without a clue.

In the ultimate analysis, DNA testing will become the order of the day only if its reliability is enhanced to satisfy the conclusive proof standard expected by criminal courts. More research work is called for to achieve this. There was a report last year that an Australian genome scientist, Dr. Ian Findlay, had developed a method of taking DNA fingerprints from a single cell, instead of the presently required 200 to 500 cells. This is expected to free samples from the risk of contamination, especially the mixing of the DNA samples of several persons.

Nothing much has been heard since then of this technique. Let us hope that the Hyderabad-based Centre for DNA Fingerprinting and Diagnostics (CDFD), which has solved many high-profile cases, will do us proud by coming out with a technique that will find worldwide acceptance.

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