I think JM chose DeMarte deliberately for different reasons in the first and second trials. In the first trial, I think it was, as you say, to contrast with Jodi. In the second trial JM also used that tactic; Demarte even upped the concept, IIRC, by reading Jodi's writings and sounding sorta like a seductive, non-librarian, Jodi. But, IMO, JM was being extremely clever as well. He could have had DeMarte elaborate her diagnosis from the first trial. He could have had her go through all that stuff about tests and numbers, etc. Instead, he had her stick to borderline, even though we all know there was a whole heck of a lot more going on with Jodi than borderline, and Demarte had no problem talking about sociopathy in the Devault trial. It's obvious the DT is going to go with borderline as a mitigator, since what else have they got to go on? (The mitigators were revealed ahead of time, too?) So, JM goes with borderline. K.I.S.S. Jodi can't stand Demarte's guts, so she's going to do whatever it takes to make Demarte look stupid, humiliate her, all of it. This is JM's plan. Because the borderline diagnosis and Demarte go together. Discredit Demarte, and you've lost your mitigator. BOOM! Jodi falls right in the trap. She even ignored the most damaging testimony entirely (e.g. premeditation, sex on the way back from the memorial service, etc), since she got so focused on the borderline stuff. What did she end up with? She thought she had a win over Demarte, but ffffft! mitigator bu bye! The jury didn't fall for borderline as mitigating. And all that premeditation testimony went unchallenged. Woh, woh, woh.....
Or something like that....
