Who killed Guy Clarendon?

Hint 1 of 14:

Frances Nolan didn't.  That much should be obvious.
There wouldn't be much of a case if she did.

Hint 2 of 14:

Don't you remember hearing about how Frances frequently blacked out?
She told you herself from Old Bailey.

Hint 3 of 14:

Think about someone who frequently dined with Frances.

Hint 4 of 14:

He probably had a special talent.

Hint 5 of 14:

I'm talking about Dr. Trevalyan.

Hint 6 of 14:

He worked for the Mesmer-Braid Institute for a while.

Hint 7 of 14:

What do you know about Mesmer?