as one famous judge said its better to have a few innocent persons in jail than guilty people on the street. Whats the betting that he would have changed his mind if it was his own family involved .
I think what is being suggested is someone - perhaps better being not on the Jury, who could sit during deliberations and advise on legal points - as I bet a lot of jurors don't want to appear stupid and keep asking the judge.
however I am guessing that is things like the forensic/ballistic/blood evidence that it is hard to understand - especially when a lot of that evidence is based on opinion - so help would not be available for that really.