Does wearing tough equipment increase the chance of a locked door happening in a case? I'm thinking of getting equipment that would drive toughness into the negative, and I don't know if it's safe to. I'm also wondering about the skill itself. I haven't got very far into the game yet, so when the cases get tougher, does lockpicking not work on some locked doors? Or is there a 100% chance of the picking the lock if the event shows up?
Gopher to the Sleuth Gods
Lockpicking is independent of Tough or Charming equipment. That is, Lockpicking, once you have that skill, will always work when you encounter locked doors. You will encounter locked doors in all your cases. One door in easy cases and then up to two doors in the harder cases.
Your scenario works for skills like interrogation (all levels), intimidation (all levels again), and pugilism. The less tough you're wearing, the lower your chances of those skills working.
Lockpicking (not to be confused with Pickpocketing), is actually a very useful skill to have. It saves you from asking two questions per case, and that can prove the difference between solving and quitting sometimes. ;-)