https://twitter.com/THR/status/644762540304674817

100 (http://www.hollywoodreporter.com/lists/best-tv-shows-ever-top-819499/item/alias-hollywoods-100-favorite-tv-820517)
Law & Order
(1990-2010) NBC

Dick Wolf's cops-and-lawyers show all but invented the procedural crime franchise. It cast huge stars before anybody knew their names (Samuel L. Jackson, Claire Danes, Philip Seymour Hoffman) and employed writers (Arrow's Marc Guggenheim and Treme's Eric Overmyer) who went on to become TV titans of their own. "It was a great show to learn how to craft a story," says House creator David Shore, 56.

Read more THR's 'Law & Order' First Episode Review in 1990 (http://www.hollywoodreporter.com/news/law-order-first-episode-thrs-818046)

Dragnet is the granddaddy of them all.

but didn't law & order last longer than dragnet?

"...all but invented..."

Other police procedure shows showed police at work (i.e. Dragnet, Adam 12, TJ Hooker), others showed a detective's investigation (Columbo, McCloud, etc.) while others (Perry Mason, Matlock, etc.)) showed defense attorneys at work and in the court rooms.
Some showed the ME at work (Quincy, that Jill Hennessey ME show).
Hill Street Blues showed police with a touch of a public defender interacting with the police commander, but few court scenes.
LA Law showed court scenes but it was all attorneys in the law farm, not police arrests, booking, etc.

Those series showed a part of the process, not the whole process, from crime to first responders to investigation to first court hearings to trial to jury deliberation.

L&O showed it all... from the street cop discovering the crime to the ME briefing the detectives on cause of death to the police psychologist explaining why the suspect may have done what he/she did, to the final sentencing.