Touch DNA: An Important Clue in Criminal Cases

Author(s): S. G. Pawar*, K. D. Mahajan, V. S. Harel, B. P. More and K. V. Kulkarni

Abstract: Advanced DNA technology, such as Polymerase Chain Reaction (PCR), makes it possible to obtain conclusive results in cases where previous testing might have been inconclusive. Polymerase chain reaction (PCR) based Short Tandem Repeats (STR) Technique becomes an important tool to solve various types of criminal cases. In 1910 Edmund Locard established the first crime laboratory as a professor of forensic medicine at University of Lyons, France and is best known for his evidence transfer theory in forensic science. According to Locard’s exchange principle hold that the perpetrator of a crime will bring something into the crime scene and leave with something from it, and both can be used as forensic evidence that means “Every contact leaves a trace." Wherever accused commits any crime, whatever he touches, whatever he leaves, even unconsciously, will serve as a silent witness against him/her. Mainly in rape-cum burnt suicidal cases improper swab samples sent by medical officer is becomes less exclusive and such silent evidence becomes challenging to find nature of crime and real culprits. DNA can be obtained from traces of biological fluids on clothing exhibits. But sometimes due to limitations in detection we can’t find out the stains of ideal biological fluids (blood, semen etc) on such cloth articles. But on the other hand, forensic expert’s interest to study the case in different way. Other than ideal fluids sometimes sweat stain detected on cloths will be helpful to establish the identity of real culprits. Mix DNA profile obtained from sweat stain on cloth articles of accused and deceased becomes a challenging job to prove involvement of the criminals. DNA sequence cannot easily be changed once the material is left at a crime scene, thus increasing its effective use in forensics, and the probability of finding an exact match. Today DNA profiling took huge strides forward in both discriminating power and the ability to recover information from any type of exhibits by extracting DNA from sweat stains on cloths also.

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