I think this is the first Perry Mason novel. You really wouldn’t know it — they’re all remarkably consistently written.
A woman married to the secret owner of a scandal magazine is caught out on a date with a prominent politician. Before much comes of that, her husband is shot to death. The woman thinks she did it herself and so tries to shift the blame alternately onto the politician and to Perry Mason but ultimately is arrested herself. Mason’s work isn’t done: he goes on to prove that, while she did shoot at her husband, she didn’t even hit him. He was shot moments later by his nephew, who stood to inherit his estate.