Thelma claims Abner was not the one who signed the will. Electra's lawyer calls Abner's brother, bail bondsman, Ralph Randy, high school dropout, to the stand to testify that he knew Abner's signature from years of living with him and to give the opinion that the signature on the will is the authentic signature of Abner Jones. Let it in because bail bondspersons are experts. Let the opinion in because it is rationally based in Ralph Randy's perception and helpful to determine a fact in issue. Don't let it in because the jurors are as capable as ordinary witnesses of drawing inferences from data.
Students allege the crash was caused by equipment design failure.
Halfhousen alleges pilot error which excuses him from paying. The students call Jed Shuckins, a thirty-year helicopter mechanic to testify as an expert on aluminum welds on the jet engine. Shuckins has never seen the helicopter that crashed and received all of his knowledge of the accident from others. Let Shuckin's testify as an expert based on his experience and knowledge. Let Shuckin give an expert opinion, because it will be rationally based on his perception and helpful to a clear understanding of a fact in issue.