Even if the seizing of assets is legit, the assets should be looked at as revenue, and should be allocated by the legislature, not the police department.
It is incredibly unseemly for police to be operating their own private economy based on forfeited assets that were acquired due to their position/power.
There should be a downside for police if the seizure turns out to not be legit. I don't think paying back double would be that out of line.