Article III, Section 2, Third paragraph:
The Trial of all Crimes, except in Cases of Impeachment, shall be by Jury; and such Trial shall be held in the State where the said Crimes shall have been committed; but when not committed within any State, the Trial shall be at such Place or Places as the Congress may by Law have directed.http://www.usconstitution.net/const.html#A3Sec2Unless the Defendant did something in San Diego, related to this attack, the trial has to be held in Tuscon. The Classic case was in the late 1960s or early 1970s, IRA arms smugglers operated out of Boston to smuggle guns into Northern Ireland. Of the several Transactions (Eight if I remember right) only one had anything to do outside of Massachusetts, and that was a phone call to Dallas Texas. The Federal Government took that one incident and decided to hold the trial in Dallas, for the simple reason Massachusetts was known to be pro-IRA and thus more likely to get a guilty verdict. The only reason the Federal Government could move the case was because of that one phone call involving the smuggling from Dallas to Boston and then only to Dallas, for it was the only city, outside of Massachusetts that had anything to do with the underlying crime.
My point is the Feds need SOMETHING to move this case outside of Tuscon and right now they have nothing.
As to the Defendant he can ask for such a transfer and it be granted if the Judge finds Tuscon to prejudice against him to get a fair trial. The problem is the Feds (and the state when they are in a similar situation) can NOT make such a move without the Defendant's permission. This came up in the Civil Rights era, Murders of Civil Rights Workers would NEVER agree to any move outside their home areas, thus you would end up with a jury full of Klansmen deciding if a Klansmen was guilty of killing a African American. The rule has its good side and bad side, but it is a very old rule and set forth in the US Constitution itself not the Bill of Rights (The Bill of Rights was added AFTERWARD, thus this has been the law since 1789 NOT 1792 when the Bill of Rights was passed).