Chucky has the perfect alibi in all eventualities
He's a CHILD'S DOLL. That comes to life and kills people with a big kitchen knife.
You see during this film how Andy has to convince his mother (which takes ages).
Then the mother sees the doll's true nature for herself and tries to convince the cop (which again takes ages).
And then the cop has to convince his mustachioed colleague (which takes a while despite his injuries).
If Chucky had mastered the art of pretending to be a child's doll, then he could've effectively seen all four of them end up in a lunatic asylum because of their "deranged belief that the doll came to life". But of course, he was impulsive and that's why his alibi failed.