How long after leaving the body does DNA remain race-able?
DNA in dried stains is remarkably resilient to degradation and can be detected many, many, many years later. The DNA breaks down if the stains are kept wet . However, the profiling techniques have become more and more sensitive and now even a few copies of degraded DNA can be amplified by PCR (polymerase chain reaction). A particularly sensitive procedure for this purpose is known as LOW COPY NUMBER. It is also possible to type mitochondrial DNA. These procedures were used to analyse the bones from the assassinated Romanov family and for obtaining a profile from James Hanratty’s exhumed body. I hope this gives you a flavour of what can now be done. Oh, and I don’t know if you asked a few days ago but you can get a profile from dried nasal secretions!
