On the contrary, it can provide a defence.

“You have a defence if you can convince the court that you drank the alcohol in question after you had driven and that you were not over the limit whilst you were driving.”[1]

With that said, your BAC can be estimated from whatever you prove you drank after the accident, which would reveal a discrepancy. Not a reliable way to get away with a terrible crime.

[1] https://www.pattersonlaw.co.uk/faqs/drink-driving-leaving-sc...