Unless Ms. Steinle was a member of a protected class such as politicians or postal workers out delivering mail, or unless the crime was on Federal property, there is no federal murder statute that would apply.
Re entering the US after deportation is a Federal crime as is being an illegal alien in possession of a firearm. So he could be charged with that.
Politics is a scam and we’re suckers for playing.
They were on the waterfront. Let’s hope they were visiting a federal port facility at the time.
They should be able to charge him with violating her Civil Rights. That is what they charge citizens with if they hold illegals for Border Patrol or do anything to stop them from trespassing or committing crimes. I know someone who was sentenced to 20 years on federal charges of violating the Civil Rights of illegals on his property.
I doubt if it works both ways, but if she had murdered him they would have charged her with that; especially if she had been found not guilty of his murder by a state court.