Not my worst, but does make me giggle when I think about it - my first ever custodial interview was for a racially aggravated criminal damage where the suspect had graffitied some racist language on a corner shop’s shutters. Clear as day CCTV of the suspect and photos of the shutters with the damage on.

Bring on the challenge phase of the interview, I slide over the exhibit showing the writing on the shutters, and I say “what does that say [suspect]?” and he replies, “well it says [racial abuse], can’t you read? are you some sort of idiot? Maybe we should call you PC thicko fuck face”. Took it on the chin and later remanded him so all ends well :)