Richard is not just arrested for being the Necktie Killer, he's tried and convicted. His unpleasantness is such that, faced with a prosecution barrister presenting evidence against him that was circumstantial at best, a jury nevertheless decided to convict him.
As far as the trial is concerned, it makes Hetty even more of a Jerkass as she could have provided an alibi for Richard as he was at her place when Babs was murdered — but she evidently chose not to. This also makes Johnny appear as even more of a Henpecked Husband as Hetty probably did not allow him to testify on Richard's behalf either, even though he knows that his friend didn't kill Babs.
And, since Richard must have told his brief that Johnny and Hetty could vouch for him, it must stand to reason that he antagonised his own defence team so much that they didn't bother to put up much of a defence, as they could (and should) have forced either or both of them to testify.
Rusk may kill all of his victims in the same way, but from what we see he disposes of the bodies differently every time. This may be well be a reason why the police haven't caught him when the film starts; in the end, he's only caught because he incriminates himself in the presence of Inspector Oxford.
When Rusk meets with Brenda, it's clear that he has been a client of her agency for some time and that she has had to blacklist him because some of the women she set him up with complained about his violent ways. Given that he has used a false name, one wonders if he had previously been a client under his own name beforehand. Even if that is not so, just how many women did Brenda connect him with — and how many of those never contacted her again?
