During my childhood the staccato musical "sting" could be heard anytime and any place that there was a parody of a detective programme or even between kids if there was a minor mystery, someone would hum the theme.
Actually watching it for the first time many decades later in very bleary prints shown on the most obscure satellite channel to fill the gaps between adverts early in the morning, its brilliance still shines through. "Everything you see is true". But how true and how was it actually made? There doesn't seem to be any authoritative account of how the scripts were written so I can only guess. Two things however strike me: firstly there is a precision and sometimes quirky individuality about the portrayal of the suspect, small but striking details of their manner and behaviour. Secondly, the calm reasonable and utterly professional cops who at all times remain dedicated, fully human and humane, sympathetic yet not presented as superheroes.
My feeling at least is that the source of the materials was not just the files but the actual cops involved who related things they'd remembered but which would not have seemed significant enough for them to include in a written report.
The most impressive was Lee Marvin playing a violent killer who combined calm petty self-absorption with lying, and unconcerned matter-of-factness about his murders. He's just violently attacked a cop, is now handcuffed and about to be taken down to the station yet calmly says he wants to clean his teeth and expects the cop, who's still got a bloody face, to hand him the toothpaste and turn on the tap. He's not trying to wind the cop up, he just wants what he wants. During questioning he says that he's hungry, is taken to a cafe and carefully chooses a meal with a special salad. Once finished he is confronted with compelling evidence, and casually confesses to a string of brutal and almost motive-less murders, then calmly turns to a discussion of how a little salt is vital to fully enjoying lettuce. It's his last meal outside jail and probably not far from his last meal on earth yet he remains calm and self-absorbed. It is the perfect outline sketch of a psychopath.
