I'm not saying every single guy requesting you stamp on their balls is a fantasist, but well, every single one contacting me has been.  Even if I thought it genuine I wouldn't accept the booking, as its just not my cup of tea, and I would be too concerned about really hurting someone; also like you say they could report you for assault or something.

I doubt any kind of liability waiver you wrote up would be worth anything in a legal situation, but perhaps someone else with more knowledge could say more on that.

I do ball busting and cock and ball torture, the thing is as you would probably have found out is start softly and increase the force in your kick gradually until he asks you to stop as for signing a waiver i think the best thing to do is ask a true dominatrix but I have never had to or been asked too.

I've never had anyone ask for this whilst I've been escorting, but when I pro dommed I had quite a few clients who did, and as I'm a bit of a sadist I loved it. 
If your client is a regular to ball busting then you shouldn't have any problems as he can help guide you. 
As xw5 says it is very intense, so providing your not wearing steel toe caps or spikes you should be pretty much ok regarding not causing any injury.  If an injury should happen then you will be liable regardless of whether you are both concenting or not.  See Operation Spanner http://www.spannertrust.org/documents/spannerhistory.asp

If he's never tried ball busting before then proceed with caution.

Hope you have fun if he turns up.
xx

Jealous as I love ball busting, but really glad you both had a good time.   

This thread caught my attention as I have a lot of request for this , most of them are out and out fantasists

I'm not saying every single guy requesting you stamp on their balls is a fantasist, but well, every single one contacting me has been.

Me too. ive actually done ball busting , but i can count them on one hand .
I too , was worried about hurting someone and been liable.

Even if I thought it genuine I wouldn't accept the booking, as its just not my cup of tea, and I would be too concerned about really hurting someone; also like you say they could report you for assault or something.

Again , me too.

With the couple of clients who have actually turned up for this , its usually people who are into heavy SnM ...Submissives , pain whores ....they will fantasize about been kicked hard in the balls with pointy stiletto boots on , but when it comes down to the real live sesh they can just about handle been kicked ( not full force!!) with bare feet , or rounded toe SOFT boots.

Theres not a chance id do it full force , or in my pointed boots , as this is bound to cause extreme pain in the very least , if not permenant damage. Id be worried about causing them long term damage and thats why its gentle kicks only ....... the clients have been happy with how I did it , its more about  the whole "mind fuck" of you looking menacing like you "could" kick the shit out them , without  , ermm , actually kicking the shit out of them

You can practice a mean looking kick that doesnt have that much force behind it ............but i woudltnt spend too much time practicing if I were you ,  as I must have been asked to do this a 100 times and only 3 have gone through with it !