“Serino is a fact witness. He’s not an expert...”
How can you say that?
He’s a 16 year police veteran and Detective. His JOB is forming an opinion on the veracity or lack thereof concerning suspects.
If he’s not considered an “expert” at forming an educated opinion on someones truthfullness than no such person exists.
I think that is the point that MOM was trying to make. It's this man's job to seek the truth and use his senses and opinion on what is true or not.
There is a bright line distinction in trial, between an expert and a fact witness. In this trial, all of the investigators and police are fact witnesses.
It would be hard for me to do justice to a decent explanation, but the fact that a cop has 20, 30 or 40 years of experience does not entitle him to tell the jury whether or not a witness is telling the truth. That's for the jury to decide.
Not to say that Serino isn't a good judge of truthfulness, he probably is very good at it. But "truthfulness" can also be determined by a jury, without resort to an expert - that's the whole point of trial/jury, to have the jury weigh the evidence.