[Mixed Trope] It really was just an accident.

CSI - S2E2: Chaos Theory: Grissom and the group are investigating the possible murder of a college student, while there are several possible signs it was a murder, it turns out it was simply a series of events that led to her death, whilst retrieving her wastebin from a dumpster to get her deposit back, a driver taking a shortcut accidentally clipped said dumpster, crushing her between the wall and dumpster, she fell in and died. When Grissom tells her parents this, they don't believe him, and claim they will hire a PI to investigate "properly"

Life on Mars - S1E3: The Stabbing: Sam and Gene investigate the apparent murder of a textile worker, who has a nasty slash across his chest, the apparent motive is revealed, the mill is poorly run, in shambles, the victim was apparently going to blow the whistle on the foreman, and the foreman confesses, Gene seems to believe it's case closed, but Sam thinks something is up. He discovers that the drive belt on one of the machines has been replaced, what actually happened is that the drive belt on that machine snapped, and struck the worker, killing him, as this would reveal the poor condition of the mill, the Foreman replaced the belt and called it in as murder to stop the mill being closed down.

The Simpsons - S5E20: The Boy Who Knew Too Much: In a funny one, Mayor Quimby's nephew Freddy is accused of badly beating a waiter, the episode revolves around the trial, and Bart being the only witness, but is reluctant to come forward because it would reveal he bunked school, eventually his conscience gets the better of him, not helped that Freddy is constantly ruining his chances by having a bad temper, and he comes forward, turns out Freddy didn't touch the waiter at all, he grabbed a bottle of champagne and walked off, the waiter was just EXTREMELY clumsy, slipping on the floor and getting himself hit by several objects in the kitchen, including frying pans, a food mixer, a toaster and several mousetraps.