In 2006, a New York State crime lab used PCR to amplify DNA from various items of evidence collected by Cayuga County law enforcement officials during their original investigation of Kulakowski’s homicide. The evidence included remnants of cotton swabs used to sample bite marks on the victim; the nightshirt stained with saliva and blood; fingernail clippings; and vaginal swabs from the victim.
To extract DNA from a forensic sample, scientists typically use chemicals to separate cells from other material, like fabric. The specific type of chemical used depends on the starting material. Then, a device known as a centrifuge, which spins samples at high speeds to separate materials, is used in combination with other chemicals help to further extract DNA from cells. DNA extraction is usually the most painstaking step of the process because it can be difficult to obtain sufficient cells in a forensic sample to yield enough DNA for PCR. Also, improperly stored samples can degrade too much to be useful. Samples can also become contaminated with foreign DNA from improper handling, which would render results useless.
In Brown’s case, the laboratory’s first report on the stained nightshirt was disappointing. Technicians hadn’t been able to obtain any DNA from the bite-mark swab. The lab’s second report was more conclusive: seven different pieces of the victim’s nightshirt contained DNA.
Moreover, the report went on to state that six of the pieces contained DNA from two different people, the victim and another person who was male.