I Didn't Mean to Kill Him

An alternative to the Motive Rant has the perp, when cornered, explain how the murder was all an accident. Their excuse can be almost anything, but the most common explanations are
 * "It was just a joke!", when a prank or practical joke goes horribly wrong.
 * They were having an argument with the victim and accidentally shoved/nudged/chased them over the precipice or down the stairs.
 * "I didn't mean to hit him that hard!": They did mean to hit him, just a teensy bit, or some such thing.
 * "I only meant to make him sick...", usually so that the victim would be unable to do something and the killer could step into the victim's place. It may be a competition, a presentation, or a trip. Or almost anything else.

After making the I Didn't Mean to Kill Him declaration, they'll often go on to explain that they dismembered the corpse and hid the pieces in a septic tank because they "panicked". In such a spiel, they will always, every time, utter the line "I didn't mean to kill him/her", as if that's supposed to make it all better.

Comic Books

 * During Infinite Crisis,  after killing

Film

 * Subverted in Legally Blonde where
 * Seymour of the original The Little Shop of Horrors says something along these lines. He even says this
 * Dorothy in the movie version of The Wizard of Oz says this about both Wicked Witches. In the book, while she may not have known water would kill the Witch of the West, she meant to throw it on her.

Literature

 * In the Dragonlance book Dragons of Spring Dawning, we find out that Berem rarely talks or even interacts with the outside world because in his mind, he's reliving the day that.
 * A subversion of this occurs toward the end of Harry Potter and The Deathly Hallows, when Harry tries to explain  Sniffle.
 * Also, in the sixth book, when Harry inadvertantly slashes Draco to bits with the Sectumsempra spell (nearly killing him), he gasps, "No- I didn't-"
 * Troubled but Cute Johnny in The Outsiders says this when he

Live Action TV

 * Buffy the Vampire Slayer, after accidently killing her mother's boyfriend, Ted.
 * An episode of CSI, Loco Motives, features a multiple murderer who explains that he didn't mean to kill anyone. He just happens to be prone to causing fatal accidents.
 * In the revelation sequence from MASH's finale "Goodbye, Farewell, and Amen", Hawkeye sobs, "I didn't mean for her to kill it! I just wanted it to be quiet!", referring to.
 * And to make matters worse,

Video Games

 * Thorvald Two-Stone in Arcanum was sent to the Isle of Despair for killing a gnome with a single punch at a bar. He is completely non-repentant, saying that the gnome had a weak neck. Thorvald did have a strength of 21, which is pretty much the maximum amount in this game.
 * One sidequest in Dragon Age Origins has you disposing of the "evidence" of deals gone bad, and by "evidence" I mean bodies. The people who killed them all give this excuse.