For that matter, every user of Tor is in the same situation.
But the premise is wrong. The police can investigate you as much as they like, they just can't assume that the traffic coming from that IP address has anything to do with anyone in particular.
You're still going to jail when you buy something with a stolen credit card and have it shipped to your house, regardless of whether you used Tor or operated a Tor exit node or are an ISP and used an IP address assigned to a customer.