As soon as police became aware that Joey and his family were missing, however long that took, one week or two, they would get Joey's and Summer's cell phone records and see that their phones went off the network early evening on the 4th and never connected again.
When they would look at Joey's bank records they would see he issued cheques on the 5th and the 8th (if they weren't backdated) but there were no other signs he was alive after the 4th. He wasn't answering or making business calls or emails or personal calls, he hadn't been seen by anyone and neither had his wife and she'd had no interactions with anyone either, but Joey was supposedly still writing cheques that got into Chase's hands.
Chase creating cheques from Joey's bank account on the 5th and the 8th BACKDATED to the 4th is prima facie evidence that he knew already by the 5th that the date would be discovered and that Joey wasn't alive and writing cheques himself on the 5th or the 8th.
At that early stage Chase never said he was writing cheques himself, he made out Joey gave them to him on the 4th, and he didn't say they were blanks. This version that he wrote them himself with Joey's permission was developed later to answer to the evidence, that's what guilty parties do with prior statements that don't fit the evidence, it's called tailoring.
MOO