He blew a 0.07 on the PBT. Did they perform another test at the police station? If so, what was the result? If not, then they are probably predicating the DUI charge on his driving conduct as opposed to BAC. What other driving conduct are they alleging to reflect impaired driving, beyond the delay at the traffic light?
What is your son's explanation for his BAC? Does he take any medications or have any medical conditions that could give a false positive? (In most cases, the reason for a test score that high when a person denies drinking is that the denial is untrue.)

