unless he drove to Colorado, there would have to be airline tickets. even if he drove, there would be credit card receipts for gas/food/motels.
somehow, they have to place him in colorado. the DA just can't say "well, he said he was there" - there has to be evidence.
Yeah, if they charge him with murder then they must have evidence to place him in Boulder. They're going to need airline tickets, motel records, etc. If not, then I would think they're arresting him as a material witness or perhaps for obstruction of justice. But 1996 is a long time ago and I think his ex-wife would need some time to recall where he was every day of Christmas season. So she could be mistaken about that.