The Texas Rules of Evidence are modeled after the Federal Rules, and Rule 404 is the main rule governing character evidence. 404(a) outlaws evidence of character simply to prove "conformity therewith on a particular occasion," I.e. you can't use character evidence to say simply "he did it before, so he must have done it now." You can't generally use a person's history of theft to prove that he committed a theft on a particular occasion, or evidence that he lied before to prove that he lied on a particular occasion. However, under 404(a) a defendant is allowed to offer evidence of his "pertinent character trait." I.e., Zimmerman could offer into evidence that he is a peaceful person. At that time, he has opened the door to character evidence that he is aggressive or violent and has so acted on prior occasions. 404(a)(2) also specifically allows evidence of the character of the victim in a self-defense case.
Florida's rule of evidence 90.404(b) similarly allows "(1) evidence of a pertinent trait of character of the victim of the crime offered by an accused, or by the prosecution to rebut the trait; or (2) Evidence of a character trait of peacefulness of the victim offered by the prosecution in a homicide case to rebut evidence that the victim was the aggressor." It is the simple fact of most assault cases, including sexual assault cases, that character evidence is extremely important. Most assault cases are of the "he-said/she-said" variety, in which evidence of aggression/violence regarding one party is gold for the other. The "Rape shield," Federal and Texas Rule 412, which most states have adopted, has severely limited sexual character evidence in rape cases, but in homicide or run-of-the-mill assault cases, the door is still wide open for evidence bordering "trial by ambush." The back-and-forth character nature of the Trayvon Martin case goes on in courthouses all over America on a weekly or monthly basis.
If you or someone you know is being investigated or prosecuted for a crime, call Board Certified Criminal Law Specialist Micah Belden at 903-744-4252.