How to get a door handle off ?

We have a lever type door handle with a lock on it, I am trying to get the handle off to see why its hanging up when we push down on it. the rest of the handles have no locks on them and a paper clip will depress the little button and it comes right off.

What's the trick to getting the locked handles off ?

Thanks

good chance its a worn out or broken return spring. really need more info.. what is the brand name ?

Same way as the others except turn the key 90° so the button will depress.

There's plenty of information on how to pick the lock available on the Internet for hobbyists, but to remove the handle I think you'd probably want to call a locksmith.