My son is seventeen and he is dating a female that is 15 years old. My son turns eighteen in November of this year. I have tried to discourage my son from seeing this girl. I have even went as far as talking to the females parents but they support the relationship between the two children even though my son will be eighteen soon. I have found out recently that they are sexually active. My son is ADHD and has the mental capacity of a fouteen or fifteen year old child. Does that make a difference or not?

In Maryland, the legal age of consent is 16. If the 17 year old male is sexually active with the 15 year old female, this is a violation of state law and if it is reported, or if he is caught with the 15 year old in a compromising situation by police, he may be at risk for arrest and criminal prosecution in either a juvenile or adult court.
3-324. §Sexual solicitation of a minor is a felony crime.

The 15 year old's parents consenting to the relationship will not over ride state law.

Determining how ADHD could be relevant in the defense of a client is something that should be researched by a licensed attorney in the state of Maryland. If case law has not been established, an attorney would have to build a defense based on facts and medical findings.