In a case of murder or rape, a forensics laboratory can, in theory, generate a DNA profile from a crime scene sample in 8 hours. In practice, though, a backlog of processing may have built up through heavy caseload, staff sickness or equipment problems. Whilst it is still possible for urgent samples to be processed within 2 or 3 days, any delay is obviously frustrating for investigators.
In the UK, a technique called RapidDNA is being trialled by a number of police forces alongside more established methods. Its USP is that a DNA profile can be generated in about an hour. This could mean that a murder suspect is arrested before he has had a chance to get cleaned up or dispose of his weapon. A burglar may be caught before he has had the chance to sell on his stolen goods.
The equipment is only the size of a piece of aircraft carry-on luggage and is just as portable. Yet it can analyse up to 4 minute samples of body fluids or cellular material left at a crime scene and deliver a DNA profile that can be searched on the National DNA Database (the UK equivalent of CODIS) within an hour. Apart from the rapidity of the analysis, there is no time lost in taking the sample to the forensics laboratory, because the equipment can come to the crime scene.
However, the RapiDNA system does have a particular limitation. Whilst it is useful for intelligence gathering and evidence screening, the DNA profiles generated using this technique are based upon fewer markers than a standard profile.
Where there is a match between a crime scene RapiDNA profile and a profile on the National DNA Database (NDNAD), the chance of the RapiDNA profile also matching the DNA profile of some unknown and unrelated person is one in a million. For court purposes, this is not sufficiently discriminating. A standard DNA profile would have to be generated from the crime scene sample back at the forensics laboratory and another search carried out.
A match between the crime scene standard profile and a profile on the NDNAD would have a discrimination of the order of one in a billion (i.e. a thousand million). To put it another way, the probability that the crime scene standard profile also matches the profile of some unknown and unrelated person is of the order of one in a billion. This statistic would provide compelling evidence in a criminal court.
Where there is a match between a crime scene RapiDNA profile and a profile on the National DNA Database (NDNAD), the chance of the RapiDNA profile also matching the DNA profile of some unknown and unrelated person is one in a million. For court purposes, this is not sufficiently discriminating. A standard DNA profile would have to be generated from the crime scene sample back at the forensics laboratory and another search carried out.
A match between the crime scene standard profile and a profile on the NDNAD would have a discrimination of the order of one in a billion (i.e. a thousand million). To put it another way, the probability that the crime scene standard profile also matches the profile of some unknown and unrelated person is of the order of one in a billion. This statistic would provide compelling evidence in a criminal court.
I've seen suggestions that writers using RapiDNA in their storylines will spoil the enjoyment of their readers or viewers because the crime will be resolved too quickly. In my opinion, this viewpoint is rather dismissive of writers' creativity. If the technique becomes mainstream, I look forward to the inventive ways in which it will be incorporated into your writing. What do you think? Will RapiDNA spoil your plots?
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