Interesting is that Trayvon Martins parents never tried to sue Zimmerman....they let the statute of limitations pass.
And, lack of money by a defendant in a homicide is never an excuse to fail to sue. Trayvon was such a violent thug...they never would get a judgment
Florida has a self defense immunity statute. He didn't use it to escape the criminal trial (probably because he would have had the same judge) but had he been sued he could ask for a hearing. A simple preponderance of the evidence that he acted in self defense would make him completely immune to civil suits over it. That wouldn't be hard to show in a case that was an easy acquittal.