DNA Profiling

DNA PROFILING (or DNA fingerprinting) compares specific regions of a person's DNA to identify them. Developed by Alec Jeffreys in 1984, it has revolutionized forensics, paternity testing, missing persons identification, and even archaeology. DNA is found in virtually every human body cell — blood, saliva, hair root, skin cell, semen. Tiny amounts (a few cells) can yield a profile.

How it works. Scientists examine SHORT TANDEM REPEATS (STRs) — specific regions where DNA sequences repeat. The number of repeats varies between individuals. Comparing STRs at 13-20 sites typically gives a probability of random match in QUADRILLIONS — practically unique. Modern PCR amplification works with even tiny degraded samples. Database systems (CODIS in the US) compare profiles to find matches.

Beyond identification. INNOCENCE PROJECT has used DNA evidence to free 375+ wrongfully convicted people in the US — many had been imprisoned for decades. PATERNITY testing. MISSING PERSONS identification. ANCIENT DNA from Neanderthal bones, mummies, even mammoths. FAMILIAL DNA SEARCHING (a controversial technique that finds relatives, leading to the Golden State Killer arrest in 2018). Privacy concerns are real and growing.

DNA profiling is one of the most precise scientific tools ever applied to law. With great precision comes great responsibility — and ongoing ethical questions about privacy and use.