As far as I know I don't think the murder weapon was ever confirmed by any of the law enforcement agencies...media hyped that it was a crowbar but it could very well have been a baseball bat.
I do think Mexico is and will cooperate in this case, IMO, if DP is taken off the table. I don't think they will want to be viewed by the American public as creating a hindrance to bringing this guy back to the US. As I recall, the Max Factor heir was given LWOP for all his rape charges wasn't he??? and he was brought back into the US from Mexico. Mexico is a predominantly Catholic country, hence no DP, but I've never heard of them having any issue with LWOP laws in another country.
Think they could set up something so wifey could let him know she wants to have communication with him in some way, so she can use whatever emotional clout she would have...him never seeing their child again, etc? Murderers have been lured out of hiding for alot less reasons. I don't believe this guy wants to spend the rest of his life on the run in Mexico. He has no money so his lifestyle won't be too good there and they are most likely monitoring the bank accounts of his relatives here. course I realize that living free and poor is better than living in prison...but I think it won't be too long now before he is brought back.