Witness for the Prosecution

Why didn't I enjoy this movie more?

I grew to love Charles Laughton as the barrister after he initially put me off.
The courtroom reparte is delightful.
There's enough B-plot for things to stay lively.

I appreciate the twist, but it ultimately felt unearned. There's too much turning in the last ten minutes, and I think my face looked like Laughton's: grimacing, slightly deflated, finally picking up my drink and walking away unchanged.