My dad passed away and they sent a check out to him befor they found out passed can i get in trouble?

Technically you could but I think the odds are in your favor. Still it's not something you should do again.

I agree with Attorney Reed. It would appear that you have no legal defense, if anyone decides to challenge this. It is not clear from your summary whether there is anyone who might do so. If you are taken to task on this, you will need to hire an attorney to assist you. James Frederick

The chances of you getting in any trouble are slim. If the maker of the check wants the money back however, you will have to return it. For instance, a social security or military benefits check paid after death (if paid for the following month which is typical) will need to be paid back to social security or the military and they will pursue collection of it.

What was the check for? That is necessary to know if its a no harm no foul situation

Yes you can get into trouble. You need to pay back the money that you took.