Here are the criteria for claiming your son. As long as he lived with you and you provided over half of his support, you can claim him. He also needs to file his return and say that he was claimed by someone else.

Qualifying child

• They are related to you.
• They aren't claimed as a dependent by someone else.
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They are under the age of 19 (or 24 for full-time students).
  • No age limit for permanently and totally disabled children.
• They live with you for more than half the year (exceptions apply).
• They didn't provide more than half of their own support for the year.