I don't believe the study asked how many family/friends obtained the firearm legally. It seems unlikely that it would be 0%.
Overall, 6.7% of prisoners reported gone through a background check when obtaining a firearm at a retail source (that's not 6.7% of the 7.5%, but rather 6.7% of all prisoners).
A "retail source" includes the 7.5% number above which is just licensed firearm dealers, but there were other retail sources I didn't include (pawn shops: 1.6, flea markets: 0.4%, gun shows: 0.8%).
Of course, the background checks doesn't really matter given that those 7.5% reported giving their actual name to a licensed firearm dealer which is what one would need to track them down.
Overall, 6.7% of prisoners reported gone through a background check when obtaining a firearm at a retail source (that's not 6.7% of the 7.5%, but rather 6.7% of all prisoners).
A "retail source" includes the 7.5% number above which is just licensed firearm dealers, but there were other retail sources I didn't include (pawn shops: 1.6, flea markets: 0.4%, gun shows: 0.8%).
Of course, the background checks doesn't really matter given that those 7.5% reported giving their actual name to a licensed firearm dealer which is what one would need to track them down.