IT was disappointing that for so many agonising days, law enforcement agencies were unable to make any breakthrough in their search for the rapist/killer in the Kasur case. If police are relying on investigating and prosecuting this case on merely a scientific basis, it should be noted that due to various reasons, some sexual assault cases are difficult to solve in the forensic laboratory.

One famous case is that of former NFL player O.J. Simpson, who in 1994 allegedly murdered his ex-wife and a waiter. The use of fingerprint DNA evidence was questioned by the Los Angeles County Superior Court. Simpson’s defence attorneys argued that the way in which the DNA samples were collected did not meet forensic standards, hence jeopardising the evidence. Because of such discrepancies, Simpson was acquitted.

Collecting and reporting authentic DNA samples as evidence against an alleged rapist is not an easy job owing to various factors which include but are not limited to the scarcity of spermatozoa in the semen samples, DNA that can easily be ruined, unscientific collection of samples, the contamination of samples during collection, etc.

In the examination of sexual assault cases, DNA typing of vaginal samples mostly occurs after differential DNA extraction. In spite of this method, DNA profiles from the seminal fraction often show the male alleles at low levels in combination with female alleles in the collected cells. This unfavourable ratio male to female DNA creates complexities in analysing DNA and use it as evidence. Another way of identifying the criminal’s biological evidence is protein analysis.

The sperm cytology test can also be used in forensic cases.

Sexual assault crimes are vastly underreported and suffer from alarmingly low prosecution and conviction rates. The key scientific method to aid in the prosecution of such cases is forensic DNA analysis. However, if there are limited resources in the forensic laboratory, and doubts about the authenticity of the biological evidence, it would be wise to rely on other investigation methods such as interrogation or intelligence-gathering.

The risks of false or misleading results from DNA identification are not cause to reject its use by crime investigators, but require caution and highly qualified technical hands to collect the evidence.

Habib Hyder Laghari

Canada

Published in Dawn, February 18th, 2018