Does he have absolutely no pec major or just a genetic deformity to the pec major?
In terms of strength, he would be a perfect candidate for single arm pushing variations. Some bi-lateral exercises would be good too, such as pushups, etc.
I am assuming it is more of a genetic variation in the size/shape of the pec major, rather than him just not having one, but I could be wrong. Regardless, if he has a significant disability due to this deformity, has he checked to see if this will exclude him from continuing onto the police academy?