skid marks

[jhankins@ix.netcom.com]

I got hit in the parking lot at work. The guy that did it has decided to be a 
jerk about it, and 
is claiming that I pulled out in front of him. Well, it was in a lot where we 
park nose-out, and I 
had pulled out of my space far enough for him to hit the rear of the car. The 
clincher, I think, 
is that he left 25 ft. of solid skid marks between the time he hit his brakes 
and hit me. Can 
anybody give me a rule of thumb to translate length of skid marks into 
approximate speed?

thanks,

Joe