Oh, I don't know about that. I think most of the reason the defense harped on the affair (and will likely again) is to prove that Suzanne was a liar - by omission. She had an emotional and eventual physical affair - which by definition means a secretive tryst. It's been said that she didn't tell her bff or sister about this affair.
When texts to SO re DA were going to be introduced (which the defense had anticipated, of course), they immediately objected calling Suzanne a LIAR. What else do they have but to try to paint her as a lying, cheating spouse. Why should SHE be believed. I believe Suzanne finally woke up and shared much more that would point to financial motive. Definitely can't have that.
I'll bet, at this point, 2nd degree is the best they're hoping for.
Some might even find his murdering Suzanne justifiable homicide (as crazy as that is).
'Flew into a rage. What husband wouldn't, right? Let's forget about all the rest, after all, he's a great guy ("I LOVE YOU SUZANNE!" - from his texts) and SM can't be trusted to tell the truth.
She was lying about abuse/financial issues while trying to justify her affair
that she told no one about' ~ the defense.
ETA: IMO