There's nothing like an ugly, messy pattern to throw you off your game. The colors? Horrific. The pattern? Disgusting. The tuck-in? A fashion crime. All around, there's just way too much going on here, and honestly, I don't know what the police would make of it all. Despite the overly-busy nature of the shirt, it seems like it would actually work if you were the murderer, the one being murdered, or simply a bystander being accused of the murder. For how ill-fitting it is, it could squeeze itself into just about any of these situations.
If you're the one doing the murdering, the blood stains will blend right in with the shirt, and if you're the one being murdered and have a prior engagement to attend right afterward, the blood stains will barely be visible. Finally, if you're a bystander on the street, you can just chalk everything up to the fact that your mother picked out this shirt for you and you felt obligated to wear it out in public.