The result has been expanded use of DNA tests amid rapidly changing technology. About equal numbers of DNA samples are sent to FBI and private laboratories. Most samples are blood or semen, but other tissues may be tested when cells can be recovered, for example, in saliva, hair follicles, and bone. The new generation of analysis uses polymerase chain reaction techniques, some of which are considered less sensitive than RFLP analysis but have important advantages for investigating small or degraded evidence samples. To maximize the best features of each approach, the FBI laboratory is turning to a combination of methods.
Defenders state that any forensic method is subject to error.
Standard-based protocols, quality assurance, and monitoring of laboratory and personnel proficiency can reduce flawed or skewed DNA test results based on technical error in collecting and processing evidence. Probabilities against a random match are estimated to range between hundreds and billions to one. Patricia Riley, Chief of the U.S. Attorney's Sex Offense Unit in the District of Columbia, reported that the admissibility of DNA evidence was upheld in 95 of appellate cases. Chief Judge Finesilver said future genetic testing will probably be used in cases involving such controversial factors as electromagnetic fields and cellular telephones as carcinogenic agents, contaminated blood, and silicone gel breast implants. For example, these cases could raise the issues of what constitutes a disability and whether a genetic trait or predisposition can qualify as a disability.