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HomeCRIMEAre hair, fibre, and paint samples– acceptable evidence?

Are hair, fibre, and paint samples– acceptable evidence?

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Since most people have visibly different hair, the community of enthusiastic forensic technicians was misled into believing that hair could be used to identify people. As we have been arguing in our previous articles, the visible difference is simply not enough for identification. Yes, we do know that people have different colours of hair; they have different textures (some are silky and smooth; some are dry and rough; some are oily, etc.). Perhaps, we can even recognize people from their backs by the looks of their hair or by a photo of the hair. However, both science and law demand rigorous proof. It is there that this ‘subjective opinion’ collapses.

There could be millions of people with similar hair. We can recognize people at times even by a photo of their eyes, lips or chin. However, once again millions could have similar eyes. Our impressions do not become scientifically and legally valid proofs.  

There is nothing in a hair

For associating hair and fibre with a crime, the underlying presumption is that Close physical encounters may result in trace transfers of hair and fibre. This is based upon an outdated principle called Locard Principle. This 19th-century gentleman gave an almost religious hypothesis that the perpetrator of a crime will bring something into the crime scene and leave with something from it. Needless to say, it is so childish an argument that it really does not warrant a discussion. He was obviously thinking in terms of the crimes of the 18th and 19th centuries when criminals had to get close to their victims. Even the native inhabitants of African and Latin America knew better. When they used blow-dart guns for hunting, they never came in contact with their prey. The same blow-dart gun can be theoretically used for murder also!

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Most importantly, the simple fact is that microscopic hair analysis by a simultaneous visual comparison of different characteristics of hair samples from two different sources through a comparison microscope cannot prove the hair came from a certain individual to the exclusion of any other person. As you can recall from the comparison of bullets and empty cartridge cases, this too suffers from the same infirmities.

Hair can be used for investigative purposes with some degree of confidence only if it is subjected to Mitochondrial DNA (mtDNA) analysis.

M. Houck et al and M. R. Bromwich have referred to a FBI study, which found that, of 80 hair comparisons that were ‘associated’ through microscopic examinations, 9 of them (12.5 per cent) were found in fact to come from different sources when re-examined through mtDNA analysis. This is a sad commentary on not only the intrinsic probative value of a doubtful technique but also on the professional competence of the self-proclaimed forensic scientists in even the pseudo-science of comparison they do.

In State v. Butler, the Wisconsin Supreme Court admitted that microscopic hair analysis was unable to positively identify individuals based on hair comparison. Also it is not possible to state what per cent of the population could have contributed that hair. In Manning v. State, the Missouri Supreme Court admitted that a microscopic examination could only suggest whether the hairs looked like the hairs of the subject but could not confirm identity. The expert could not claim that the hair ‘matched’ that of the defendant, but only that the hair came from a member of the black race. In State v. Ware, the Wisconsin Supreme Court concluded that hair comparison was ‘not capable of individual identification’.

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In People v. Linscott, the Illinois Supreme Court held that even if 12 characteristics of hair (for example, pigment, thickness, condition, root, tip, etc.) are compared, all that can be said at best is that the hair found at the scene or from the body is ‘consistent with’ the samples provided by the defendant. Consistent here means no dissimilarity. It does not mean that the person can be identified with the hair he might have left behind. In McGrew v. State, the Nebraska Supreme Court had concluded that such evidence was more a ‘matter of the observations of persons with specialized knowledge’ than “a matter of ‘scientific principles’.

The National Academy of Sciences Committee points out that no scientifically accepted statistics exist about the frequency with which particular characteristics of hair are distributed in the population. There appear to be no uniform standards on the number of features on which hairs must agree before an examiner may declare a ‘match’. The committee found no scientific support for the use of hair comparisons for individualization in the absence of nuclear DNA.

Examination of fibres is on even weaker footing

Fibres fall into two broad categories: natural and synthetic. Both types are used in the manufacture of commercial products of a wide variety, ranging from all types of apparel to seat covers, and home, office, and automobile coverings. Natural fibres are divided into three categories: animal, vegetable, and mineral. Animal fibres used in commercial production include wool, silk, camel hair, and a wide variety of furs. The vegetable category contains such fibres as cotton, linen, hemp, sisal, and jute. Cotton is the primary fibre used in commercial applications. Fibre materials classified as minerals include asbestos, glass wool, and fibreglass, etc. Synthetic fibres include acetates, acrylics, aramid, modacrylic, nylon, olefin, polyester, PBI, PBF, rayon, spandex, sulfur, and vinyon, etc.

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Fibre cases differ from hair cases in that the initial determination of its basic character is significantly more complex than determining if a human hair was male, female, Caucasian, Negroid, or Asian, and from what portion of the body.

The weaknesses inherent in fibre evidence are therefore greater. Since fibres are produced commercially, it means that they could be found in billions of other places too. As with hair, in case of fibre also, we can only speak, at best, in terms of ‘similarity’, ‘consistency’, ‘lack of dissimilarities’ or the like—to speak of ‘matching’ is an unscientific farce.

The National Academy of Sciences pointed out that there have been no studies of fibres (for example, the variability of their characteristics during and after manufacturing) from which inferences could be drawn about their individuality. Similarly, there have been no studies to inform judgments about whether environmentally related changes discerned in particular fibres are distinctive enough to reliably individualize their source, and there have been no studies that characterize either reliability or error rates in the procedures. Thus, a ‘match’ means only that the fibres could have come from the same type of garment, carpet, or furniture; that is, it can provide only class evidence.

In State v. Goney, a rape case, the Wisconsin Supreme Court held that the presence or absence of hair or fibre evidence from the couch, on which the rape was said to have taken place, could not help the prosecution or the defence. Corroborating evidence was necessarily required. Conventional police investigative sense should never be abandoned in the face of forensic evidence.

In Williams v. State of Georgia Supreme Court, the defendant Wayne Williams was charged with the murders of 12 young African-American males. In this case, the victims had fibres that were linked to the fibres of the carpet at the home of Williams and also at the floorboard of his car. Justice Smith, however, pointed out that the fibre evidence provided no information as to the murderer’s technique in killing or disposing of his victims nor could the experts explain the exact mechanism of the alleged transfer of fibres from Williams to the victims.

From the fibre evidence, the best that could be inferred was that each of the victims possibly was in contact with Williams, his house, or his car sometime before his death. He pointed out that it would be possible for the murderer to apprehend, kill, and dispose of his twelve victims in dissimilar ways, yet transfer fibres to them in each case.

The readers can see for themselves that for all such things, I am obliged to cite judgments of the American states’ Supreme Courts. Why? The reason is that because the legal fraternity there is scientifically more ‘aware’, they raise questions and doubts.

In the UK, for example, the Royal Society of Edinburgh has published a small but self-contained book ‘Forensic DNA Analysis: A Primer for Courts’ specifically for educating the Courts about this complex science. Has any similar effort been made in India regarding any forensic technique? No!

Such questions are not even discussed in Indian courts. Here a science graduate makes a pompous claim regarding ‘matching of hair or fibre’ and the defence, the courts, everybody accepts that as the final word. If at all the courts call for some so-called self-styled experts from outside, they try to obfuscate the issue as much as possible with their vested interests in mind. You can rest assured, not one of the police officers, so-called forensics and defence lawyers know such things. Because the ‘lack of wisdom’ of forensics is not challenged in courts, we do not have any High Court or Supreme Court judgment on them. In the end, justice suffers.

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Dr N C Asthana IPS (Retd)
Dr N C Asthana IPS (Retd)
Dr. N. C. Asthana, IPS (Retd) is a former DGP of Kerala and ADG BSF/CRPF. Of the 51 books that he has authored, 20 are on terrorism, counter-terrorism, defense, strategic studies, military science, and internal security, etc. They have been reviewed at very high levels in the world and are regularly cited for authority in the research works at some of the most prestigious professional institutions of the world such as the US Army Command & General Staff College and Frunze Military Academy, Russia. The views expressed are his own.


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