You can't. The legal system moves very slowly. The only way to get to a quicker resolution is if the facts are such that the defendant is willing to settle.
It isn't like TV where the client walks in and 48 minutes later the matter is resolved.
It really depends on what the items are... Is it just regular household items? Like clothes and other personal belongings? There's no criminal issues that would apply to this situation, as long as it's not something that would be registered with the state (car, boat, guns, etc) and none of the property is illegal to own.
You could be sued civilly for the cost of the property though. I'd really check with an lawyer about this one, since it's a civil matter. I'm not an attorney, but I can't think of any Michigan criminal laws that would apply, only civil laws.
I'd guess that if you mailed them a certified letter in the mail, and give them an appropriate amount of time to pick the items up (say 90 days to be generous), you'll be okay. That way you'd be able to prove in court (if you're sued) that you were more than generous and gave them more than enough time to pick up their stuff, but they refused to.