Yes you may claim your son as your dependent if all of the following conditions to one of the two IRS tests below have been met. The time your son is in custody would be termed "Temporary absence" away from the home (residency test) because he is probably expected to return. (See this Link - https://apps.irs.gov/app/IPAR/resources/help/tempabs.html)
A parent may claim their child if they meet either the qualifying child or qualifying relative test as outlined below:
Qualifying Child
These 5 tests (all of them), will qualify a child as a
dependent:
-
Relationship: They
must be your child, adopted child, foster-child, brother or sister, or a
descendant of one of these (grand or nephew).
-
Residence: They
had to live with you in the same residence for more than half the year.
Being away at school is considered as living at home.
-
Age: Must
be under age 19 or under 24 and a full-time student for at least 5 months
of the year. They can be any age if they are totally and permanently
disabled.
-
Support: child
did not provide more than half of their own support during the year.
-
Joint
Support: The child cannot file a joint return for the year.
Qualifying Relative
These 4 tests (all of them) will qualify a relative as a
dependent:
-
Not Qualifying Child: They are not
your or another taxpayer’s “qualifying child”
-
Gross
Income: Dependent has to earn
less than $4,050 in 2016.
-
Total
Support: You provide more
than half of the total support for the year.
-
Member
of Household or Relationship: The person (a friend, girlfriend,
non blood relative) must live with
you all year as a member of your household or be one of the relatives
that doesn’t have to live with you (mother, father, brother, sister, aunt,
uncle, stepmother, stepfather, your child, stepchild, foster child,
adopted child, etc) Note: this list is not all inclusive.
