Forensic DNA Testing

There are two main types of forensic DNA testing. Called, RFLP and PCR based testing, although these terms are not very descriptive. Generally, RFLP testing requires larger amounts of DNA and DNA must be underrated. Crime-scene evidence that is old or that is present in small amounts is often unsuitable for RFLP test. Warm moist conditions may accelerate DNA degradation rendering it unsuitable for RFLP in relatively short period of time.

PCR-based testing often requires less DNA than RFLP testing and the DNA may be partially degraded, more so than is the case with RFLP. However, PCR still has sample size and degradation limitations that sometimes may under-appreciated. PCR-based tests are extremely sensitive to contaminating DNA at the crime scene and within the test laboratory. During PCR, contaminants amplified up to a billion times their original concentration. Contamination can influence PCR results, particularly in the absence of proper handling techniques and proper controls for contamination.PCR are less direct and more prone to error than RFLP. However, PCR has tended to replace RFLP in forensic testing primarily because PCR based tests is faster and more sensitive.