Could be. He might be trying to put Brown at ease so she'll talk more. He might be tempting her to lie, etc. I'm sure he was looking for witnesses who could say the words heard during the fight, and he might have just been relating that if there's any issue coming from Zimmerman, it doesn't appear on the record (no witness heard any racial stereotyping from Zimmerman).
Anyway, I added that remark in an attempt to be thorough in disclosing what has been reported about Serino's attitude and remarks. He also said something to Tracy Martin on Feb 27 along the lines of trying to catch Zimmerman in a lie. So, here's Serino, telling Tracy that he's the lead investigator into Trayvon's death - of course he's going to try to give assurance to Tracy that he (Serino) isn't just accepting Zimmerman's story - he's paid to be a skeptic and rational thinker.
Exactly.
I’m on your side, relax, vague phrase that opens the person being interviewed to reveal information.
Remember that one of the fathers of the two who hammered the fifty year old was involved in a black racists group, maybe he just wanted to know Tracy Martin’s racial opinions and that was a way to start the conversation.