Thursday, October 2, 2008

DNA Technology

by Connie Park

The days of “good old-fashion” detective work just got better! The advancement of technology in DNA testing has proven to be a powerful investigative tool for law enforcement and it has become an established part of criminal justice procedure. DNA testing has been utilized in identifying suspects of violent crimes, missing persons, and to exonerate innocent people who have been falsely convicted. There were more than 17,000 cases involving DNA evidence last year in the United States. DNA test results are common today in courtrooms due to reliability of the tests.

DNA testing allows the application of science to law. DNA is the chemical deoxyribonucleic acid, which stores the genetic code of each individual person. With the exception of identical twins, each person’s DNA sequence is unique. In addition to blood and semen, substances such as saliva, teeth, and bones can be sources of DNA. The listed biological evidence contains white blood cells where DNA is found. It allows us to analyze “invisible” evidence collected at crime scenes such as perspiration on a suspect’s clothing, skin cells on a ligature, saliva on a drinking glass or cigarette butts.

After a DNA profile has been developed, the profile is entered into the CODIS system (Combined DNA Index System), which is a national databank. CODIS is a computer network that connects forensic DNA labs at the local, state, and national levels. CODIS will alert the system whether or not there is a match of that DNA profile in the databank. In 2000, the DNA Backlog Elimination Act required the majority of all States to collect and test DNA of defendants convicted of homicide and sexual assaults.

DNA testing has transformed the way we solve crime and handle criminal investigations, but just as importantly, it allows no room for any errors. It has helped in solving many difficult cases and has discredited eyewitnesses' statements and physical evidence recovered at crime scenes. Through the use of DNA technology and DNA databanks, homicide cases from more than 25 years ago have been cleared. Investigators are able to request DNA testing on biological evidence where testing was not performed or was unsuccessful in years passed. In addition, DNA technology allows to test old, unpreserved, and microscopic bits of substance that could result in an accurate DNA reading.

In 1984, a 14-year-old female was found in an abandoned building sexually assaulted, strangled, and bound. A suspect was developed during the investigation but investigators were not able to file charges. In addition to an eyewitess's statements, the complainant was last seen alive with the suspect. Due to DNA technological advancements, biological evidence was tested and a suspect was identified and charged. Frederick Johnson was charged with capital murder and is awaiting trial.

Kerry Max Cook, author of Chasing Justice and a guest contributor at Women In Crime Ink, was charged with sexually assaulting and murdering Linda Jo Edwards. After 22 years in prison falsely convicted, Kerry was exonerated by DNA testing that identified James Mayfield as the real killer.

DNA technology couldn't have come soon enough.


jigmeister said...

Good post Connie. Perhaps you could do another on the number of occasions where DNA, though present at the scene or on physical evidence does not solve a crime, yet juries expect it in every case. How does it make your job, as a homicide investigator harder on those many occasions?

A Voice of Sanity said...

They just tested the remains found in Dr Crippen's coal cellar - supposedly from his murdered wife. Turns out they were from a man's body. Oops. Sorry Doc!

Connie said...

Thanks Casey....great question. We've investigated murder cases where biological evidence was collected and tested. There were DNA profiles developed and entered into CODIS, however, no matches were developed. If there are no suspects to compare the DNA profile to or the suspect's DNA profile is not in the CODIS databank, the potential of the biological evidence is limited.

Television shows like CSI have impacted the way jurors interpret evidence and facts of the case. Jurors believe what they see on CSI is realistic and believe the technology and resources are available to law enforcement. We've be on crime scenes where people have requested evidence be tested immediately at the scene because they've seen it on CSI. I drive around in a Hummer to crime scenes and solve all murder investigations within an hour.

A Voice of Sanity said...

Connie said...
Television shows like CSI have impacted the way jurors interpret evidence and facts of the case. Jurors believe what they see on CSI is realistic and believe the technology and resources are available to law enforcement.

IMO this is a myth. The reality is that far too many jurors believe that what the prosecution and their witnesses say is backed up by 'CSI'. So if the prosecutor says, "Item A clearly matches item B" the jurors assume it does, and if the defense objects (and many fail to) and wants proof they are dismissed by the jury as just "slick lawyers with smoke and mirrors".

jigmeister said...

Certainly there is skeptism of defense attorneys but that skeptism extends to both sides today.

Having tried many many cases over 30 years, I can tell you that since the introduction of DNA, TV's depiction of the ability of DNA to solve all crime, has created heightened expectations of proof on the part of juries. This has dramatically changed the job of the homicide investigator, prosecutors, forensic specialists, and even medical examiners.

Remember that DNA is deposited by everyone innocently all the time. Also many scenes have absolutely no DNA or occur in public places where DNA is contributed by hundreds of people.

Though DNA has been a great boon to law enforcement, what people see on CSI is a gross exaggeration of the ability of DNA or forensics in general to solve crime, but the average juror doesn't know that.

I guarantee that Connie does!

FleaStiff said...

Much of the dna backlog is administratively driven. Some poorer counties complain that they have neither the scientific knowledge nor the funds to properly store dna evidence that the law requires them to store.

One bright glimmer of hope for a more rapid elimination of any dna backlog and a tremendous reduction in the cost of dna processing is the universal quenching probe technique announced in Japan last week and presented in an American Chemical Society paper.