Here's an article that generally addresses the issue:
How Colorado Courts Handle Multi-County Criminal Cases. But in terms of specific statutes and rules, I am not sure there is an easily accessible, definitive set. The article stresses the complexity of the decision and the importance of communication and working relationships among jurisdictions as the key to avoiding adverse outcomes.
Under existing principles of jurisdiction as I understand them, it is sufficient for legal purposes that part of the criminal conduct occurred in the 12th Judicial District. Subject matter jurisdiction is solid because a part of the criminal episode clearly was committed there. Since Morphew is no longer a resident of Colorado, the allegation that he disposed of his wife's body in the District is sufficient to give courts there personal jurisdiction over him. I doubt that he will contest jurisdiction in the 11th JD.
Venue is another matter. If Morphew can present evidence that he cannot receive a fair trial in Alamosa, he can argue for a change of venue within the district or to a larger metropolitan area in Colorado. He did this successfully in Salida.
Even so, it should take evidence of a pervasive community prejudice against him to justify a change of courts before the jury selection process is complete. Most judges prefer to assemble a larger than normal jury pool and assess the impartiality of each juror during
voir dire. I disagreed with Judge Lama's decision to transfer venue within the 11th JD because although a few people testified, evidence of
pervasive prejudice in the community was lacking.
I have no doubt that conversations were held between and among representatives of the 12th and 11th JDs - and probably the state AG's appellate unit, as to which district would be most appropriate. I think the civil lawsuit Morphew brought against 11th JD officials, the issues the pending case could present for the credibility of the case, and the lingering controversy over the DA there was a serious consideration.
Sorry I can't come up with a more definitive and satisfying answer, and even the above response could be wrong!