Unfortunately, despite a great start, DNA collapses into increasingly far-fetched improbability planted DNA, fugue states where Tom Conti comes around in the midst of a murder scene and cannot sure if he did it or not, the son capturing crucial evidence on video, the wife having affairs with both the murder victims, a possibly innocent criminal from Contis past who may or may not be conducting the new killings out of revenge. About the point in the second episode [SPOILER ALERT] where all of this is revealed to be the activity of a jealous detective who is planting the evidence to incriminate Tom Conti because he desires Samantha Bond for himself, the entire house of cards comes tumbling down. This revelation comes far too early in the story it should have been a last minute twist. Moreover, one can see how contrived it is as the moment this twist comes all the other red herrings the wifes affairs with the victims, Tom Contis fugue states, the suspect from the past drop off and are forgotten about.
However, the improbabilities keep increasing Tom Conti making a ridiculous return from the dead after seemingly being banged on the head and dumped in a reservoir, whereupon he and an assistant investigator team up to taunt and implicate the guilty party by planting evidence. Unfortunately, plot devices like these, which belong to the classic psychological thriller, jar when introduced to the much more realistic form of the forensic thriller. The forensic thriller and its focus on the minutiae of evidence and behavioural psychology has made the improbably contorted plots of the psycho-thriller a thing of the past. By the end, when the killer is finally apprehended, the plot has becomes so contorted that any case that might have emerged would have been thrown out of court first of all, the police have allowed a civilian to trample all over the crime scene, and secondly not one but three different forensic investigators have all been planting and falsifying evidence in order to implicate one another.
DNA was later expanded out into a tv series Donovan (2005), which consisted of three episodes only that were 90 minutes apiece. These featured return performances from Tom Conti and Samantha Bond, although these were standard crime dramas featuring Tom Conti as an investigator and his blackouts were written out.
Clip from the film here:-