DNA Identification

An increasing number of TV programs are including efforts by private investigators and detectives to attain a proper DNA identification. Sometimes that identification involves a recent murder; sometimes it involves a “cold case.” In either instance the TV viewer normally gets only brief and fleeting glimpses of the sort of laboratory work that must go into the making of that DNA identification. That lab work calls for performance of a long and tedious process, a process that would make for “boring TV.”  That process is explained in the following article. The writer has previously worked in a molecular biology laboratory.On the morning of January 12, 2007, residents of Los Angeles County who watched the local news viewed footage about ongoing efforts at DNA identification. The news report that accompanied that footage focused on the County’s need or more laboratory personnel. The County labs had been flooded with demands for DNA identification.

The first statistics released in that televised report indicated that a backlog of close to one thousand specimens sat in County labs awaiting the process that would lead to DNA identification. Follow-up information disclosed more details on those specimens. While all were specimens from rape cases, only a small percent of those specimens were from cases where a rape victim had not known her attacker.

The report underscored the need for DNA identification in rape cases where the name of the attacker remained a mystery. The report suggested that the County planned to concentrate its efforts on completing the analysis of those specimens without a link to a known rapist. Due to the brevity of the report, the TV viewers heard and saw nothing about the County’s use of computerized DNA identification.

Such computerized DNA identification facilitates the attempts by law enforcement officials to link a DNA profile to the name of a known rapist. Yet the lengthy process needed for DNA identification can not be accelerated greatly through the aid of a computer. That process requires a surplus of time and personnel.

Laboratory technicians must carefully remove a tiny sample of fluid from each specimen. That tiny sample, what the technician will refer to as an “aliquot,” must then go into a designated well on a laboratory plate. The technician must make certain that the aliquot from each specimen goes into the proper well.

The plates are then run through a PCR machine. That machine carries out a polymerase chain reaction on the materials in each well. Using that reaction, the PCR machine can expand the size of the DNA information within the genetic material that lies in the liquid specimen. That specimen typically contains a sample of semen, saliva or blood.

By expanding the size of the DNA information within each well, the PCR machine allows the laboratory to decipher the DNA code of any victim’s assailant. Now the reader must understand that a DNA code is not a secret message with just a few letters. A DNA code is a long and detailed message that instructs the cell how to make its vital proteins. Examination of the details in the DNA code is aided by computerized DNA identification.

The computer can quickly sort through the database of DNA codes for known and captured rapists. The computer then seeks to match those codes with the DNA code of the examined specimen. A match can provide a D.A. with important evidence.