The legal chain of custody does not start until the first law enforcement officer takes possession.
That's exactly right... and those law enforcement officers (Doughty and Dhority) later both positively identified the two shells as the shells turned over to them by the Davis girls.
A proper chain of possession must be maintained from the time it is collected by law enforcement personnel to the time it appears in court.
These clowns can claim there is a problem with the chain of custody, but any clown can make any claim they want, no matter how hollow, unfounded and wrong the claim is. It is another thing entirely to actually show what the chain of custody problem is.