<P> A defensive three - second violation , also known as illegal defense , is a basketball rules infraction in the National Basketball Association ( NBA ) introduced in the 2001 -- 2002 season . It is assessed when a member of the defending team spends more than three seconds in the free throw lane ( also known as the 16 - foot lane , or colloquially as `` in the paint '' ) while not actively guarding an opponent . To be considered actively guarding , a defender must be within arm 's length of an opponent and in a guarding position . A three - second count is suspended if : </P>
when was the defensive 3 second rule implemented
the 2001 -- 2002 season