It really depends on the item, I think. If it's an item of little value, then I think I'd let it go, as well as the friendship. If it was an item of some worth (an expensive piece of jewelry, or a computer, or a car, or a large sum of money, then I think I'd report the theft to the authorities and find a new friend.

Unless you have video of them actually committing the crime, then it's just your word against your friend. If you don't have video, I would confront them in the presence of at least one other adult, because there isn't much the authorities are going to do about it if you don't have physcial irrefutable proof of the act. Plus, you will feel better to have confronted them. They will more than likely lie to you, so, just be prepared for them to do this. Regardless, they are now your EX-friends because you need to let them go as friends. They were not your friend to begin with if they took something from you.

If you DO have video of them stealing the item, then, I suggest you do NOT confront them. Report the theft to the police along with the video evidence (make a copy of it) and wait and see what happens. The reason you don't want to confront your ex friend in this instance, is they could just deny it, and dispose of it. It's more likely they still have the object in their possession, and can be caught with it (hopefully). Letting them get their just rewards will be more valuable to you in the long run, because you cared about them. If you do nothing, then that means you never cared for them at all. If that is is the case in truth, then just do nothing.

Of course I'd confront them. When you say that I know beyond a shadow of a doubt, I assume you mean that I have actual proof, because I'm a suspicious person. And when you say "of value," well, that narrows the field down considerably. Even more than the value of the item, though, is the value of my trust in my friend, which would have been lost. I have high standards for my friends, and you bet I will be saying something.

So I'd go right up to them and tell them that I know they stole it, that they had better explain themselves, and unless they have a very good explanation I am going to the authorities. I'd make sure they know how disappointed I am in them. And hopefully they'll feel some remorse.

I definitely would. I'm assuming this would be something like a watch or a pair of shoes. If I had proof that they had the item, they're caught. None of the "valuable" items I own have high production runs, so they chance of them owning a similar or identical item is right about zero. If they denied it, I'd have to consider what options make economical sense, as well as whether or not I'd be prepared to really go after them by spending more money.

Yes, and then you never speak to them again. I had a friend stay with me once when she was out of a job. She stole a coin collection, and had the nerve to pay for her groceries with the coins right in front of me. I never said anything to her, but it always bothered me. Years later, during an argument where she was calling me selfish, I threw it at her, and not in a nice way. I also asked her what else she had stolen from me and others through the years. I could tell by the look on her face that she was guilty, and that I should have ended the friendship long before. I cannot abide a thief. If she had asked, I would have given her anything I had. The fact that she stole from me has stayed with me for many years. She once tried to reconcile with me, and I refused.

Unless I had actually seen my friend steal from me, I could not be 100% sure. If I was convinced that I had enough evidence and reasoning to truly think he/she stole from me, I would confront the friend, but know going in that whether I am right or wrong, the friendship would be over after that confrontation. I think I would want to weigh my "100%" certainty against losing that friendship. If the item was something of little to no value, or the friendship was very valuable to me for some reason, I would also need to consider that. But again, unless I had conclusive proof, I would want to think long and hard before calling my friend a thief.