Borrowing things from a neighbor or friend isn't something that you might think will lead to issues down the road. But, what if you forget to return it? Most of the time, the person will remind you that you have their things; however, some might decide to take the petty road and report the item as stolen. This could open you up to criminal charges relating to theft of merchandise.
For the most part, forgetting to return something isn't going to lead to criminal actions. Criminal laws stipulate that there must be an intent to deprive the actual owner of being able to use the item you have. This usually isn't the case when you forget to return something that you borrowed. Typically, people don't borrow items from friends or neighbors with the intent to keep it forever.
When you are charged with theft in any case, the prosecution has the burden of proof. They must prove to the jury that you took the item with the intent to keep it forever. This can be hard to do because all you have to do is to introduce reasonable doubt into the mind of each juror. You can address small points that can do this, so don't think that you have to wait for something major to try to find your defense angle.
Your defense strategy should address the specific claims of the prosecutor. No matter what the situation is behind the charges, you should look at the options so that you can come up with the plan for how you will address everything.