Testimony about the general behavior of certain kinds of offenders is not admissible as substantive proof of defendant’s guilt. Every defendant has the right to be tried on the evidence against him, not on the general characteristics of other criminals. Evidence that the defendant was acting in a certain way may give rise to suspicion, but it is not admissible to prove that he committed a crime.
An LEO cannot testify that it is common for drug traffickers to use rental cars rented by a third person. Allowing that testimony gets reversal.