The only way to start a blog about TV detectives is with Columbo. He remains the iconic police detective of the 20th century, and that's because of several important things. Firstly, Columbo retrieves the credibility of the police detective, after a spate of amateur detectives had rendered the police useless. Why do you need Japp when you have Poirot, or Lestrade when you have Holmes? For the paperwork, mainly.

But Columbo brings us back to the idea that the best person to solve a crime isn't a charming amateur, it's the detective in charge of the case. He plays low-status, even when he's up against a murderer. He wears a beaten-up raincoat, and under it, he's usually wearing a suit in a colour somewhere between brown and pink, which only existed in the 70s. He looks so shambolic that on one occasion, he is mistaken for a homeless man by a nun (Negative Reaction, season 4).

He has a squint, because he's blind in one eye (and before Baddiel and Skinner fans write in, yes, Columbo has a glass eye. It's not just that Peter Falk does. In the 25th anniversary episode, A Trace of Murder, Columbo asks someone to join him in an interrogation, remarking that 'three eyes are better than one').

And, of course, he never knows anything about the world into which this particular murder has thrown him. Mrs Columbo might be a fan of this murderer's books, or songs, or films, or whatever, but Columbo? He doesn't know anything about this kind of thing. It's a deeply contrived ignorance. Columbo doesn't need to know anything about film projection to catch a man who murders the projectionist, because he knows the only thing that matters: the human condition.

Columbo stands in a direct line from Bucket in Bleak House, and Porfiry in Crime and Punishment: he is the dogged detective who just won't give in. Like Porfiry, he simply knows who the guilty party is, because his grasp of psychology is supreme.

But Columbo is also structurally ground-breaking. In the first 15-20 minutes, we see the murder committed, and we know whodunit. The reason we keep watching is to see Columbo unpick the tiny mistakes the murderer has made, and catch his killer. He doesn't always have any evidence, and he won't always get a conviction, but he knows – and more importantly, the killer knows – that Columbo has solved the case.

This structural shift means we begin every episode with the killer's perspective. And while sometimes they are unremittingly vile – being played by Robert Culp, Jack Cassidy or Patrick McGoohan is usually a bad sign – it also means that we have sympathy for the murderers who are facing a blackmailer (Johnny Cash, Swan Song, season 3), or losing their marbles (Janet Leigh, Forgotten Lady, season 5).

Is he iconic? You betcha. The raincoat, the catchphrase ("Just one more thing" – borrowed by the late Steve Jobs to close out his keynote presentations), the references to the never-seen Mrs Columbo, the dog, Dog, the car that looks like it will implode from rust.

Are there any duffers? Well, I can't deny the episode where a man's alibi is that he was caught by his speed camera, and it turns out to have been his secretary wearing a photocopy of his face, is hardly a classic.

But, ultimately, do you want Columbo to investigate your murder? Yes.

That of a family member or friend? Yes, but only if you didn't do it.