DNA profiling advancement - the use of DNA profile in solving crimes

FBI Law Enforcement Bulletin,The, Feb, 1998

In October 1997. correctional officer Iran Shuttlesworth was convicted of the kidnapping and first-degree sexual assault of a Milwaukee woman. As they do in many crimes. examiners from the FBI Laboratory had compared the suspect's DNA to that of a semen stain found on the victim's clothing. At the trial. an examiner testified that the FBI had identified Shuttlesworth as the source of the semen stain.

This case represents a major breakthrough for DNA evidence. Although recognized as the genetic blueprint for an individual, in the past, DNA tests could do no more than show that an individual could not be excluded as a possible source of an evidence stain. Sometimes the odds of another person in a given population having the same DNA were astronomical; nevertheless, scientists could not positively link a specific person with a particular evidence stain.

Improved profiling techniques, as well as an unparalleled statistical base, provide the framework for this scientific breakthrough. In a process known as Restriction Fragment Length Polymorphism (RFLP) typing, FBI scientists generate DNA profiles from six sites, or loci, on the DNA molecule. These loci provide enough information to compare with the DNA profiles from evidence stains and declare a match. Experts then compare the matching profile to various population groups and calculate the likelihood of selecting an individual from the population with a similar profile. If that number proves exceedingly rare. the suspect can be named as the source of the evidentiary stain. The ability to do so testifies to the FBI's statistical methods. In addition. improvements in RFLP typing have allowed the FBI to examine six loci in less than 2 weeks, a process that once took more than three times that long and involved only four sites. Moreover, once DNA testing required relatively large stains with high-quality DNA, and it took weeks to reach a conclusion. Today, however, FBI scientists can type DNA from the back of a postage stamp, the shaft of a hair, and the end of a cigarette in a matter of days. Over a decade of research paved the way for the FBI's ability to match suspects to evidence stains.

Now the equivalent of molecule fingerprints. DNA profiles have indeed proven to be valuable investigative tools. As the FBI Laboratory continues to develop innovative technologies and share its expertise with criminal justice professionals worldwide, it takes great strides in bringing offenders to swift and sure justice, while clearing innocent individuals and protecting crime victims.