Yeah but surely, somewhere around the park there'll be a CCTV cam with you on it. Walking into the park or walking out, the police'll send out a wanted poster and they'll get you one day.
Possibly.
I'll have to cover my face with something...
Erm, I mean, theoretically. Obviously.
Hmmm.... it would be a tricky one - you'd be better off leaving the knife at the scene - having a bloody knife at home may be a bit of a giveaway. You'd also have blood on your clothes and therefore the issue of disposal of them (black bag & bonfire?) . There is also a high likelyhood that when you got changed you'd have the trace evidence of blood on your skin which isn't as easy to get rid of as you might think. (blood under your finger nails) etc.
If it was in a park you'd have trace evidence of your shoes linking you to the scene - shoe prints/transfer of materials etc.
I'm onto you "Stabby Stevo"