Brake lights stay on

Four cylinder front wheel drive automatic 140,000 miles.

Unless I disconnect my battery, my brake lights stay on. I have read that it might be the brake light switch or even just the little button might be missing. I taped a penny (in what I think is the right place) but the lights stayed on. Is there any way I can be sure what the problem is without replacing the brake light switch (seeing as how it is not very easy to get to)? Any help is appreciated. Thanks