Unfortunately this is a big problem all over the country. I cant tell you how many calls I respond to on a weekly basis regarding these types of crashes. The big hang up is that most local and state governments do not have any laws regarding the detention and/or deportation of confirmed illegal aliens. The state government advises that illegal aliens are a federal problem the federal government then intern advises that its up to each state to enforce it. But with most states not having any laws in place nothing gets done. The federal agency ICE can deport but is extrememly undermaned and does not have the resources and man power to deport everyone that needs to be around the country, they also usualy only get involved when the illegal alien is found guilty and sentenced for violent crimes. But again once the illegal alien serves his/her time in prison and is deported they can easily just change their name and come back accross the border.
Sorry for the lenghty post, but I feel for the victims of these crimes and figured i would add my 2 cents.