Honestly, I think the idea of using a dead man's hand to put their fingerprints on a knife is something out of a bad mystery novel.
In reality, first you'd have to first wipe your own fingerprints off the bloody knife, then wrap the dead man's fingers around it in a convincing way so that his pressure and grip make it seem like he was the killer. His clothes and hands should have blood spatter from the stabbing, so you'd have to fake that in a realistic way. And of course you'd have to wear gloves because if your own fingerprints were on his hands, it would give it away. After setting up the crime scene you'd then dispose gloves so the police don't find them. And remember, there was a child in the house while all this was going on.
To do all that in a way that wouldn't be obvious to the cops is next to impossible. There are a hundred ways it would be obvious that the crime scene was manipulated.
