They should issue him a warning, just for being honest and not pulling some lame “my speedometer is broken” routine.
I once went to traffic court to testify about an accident I had witnessed and while there one dude, cited for driving a 100 mph, tried to pull that "my speedometer was broken" bit. After the judge quit laughing, he said, "You cannot tell the difference between 55 mph and 100 mph? The defendant is found guilty and will serve one month in jail and pay a $500 fine."
Funny.