Is it legal to use a K9 on a juvenile (use of force issue)?

Yes. In Melgar v. Greene (4th Cir. 2010) 593 F.3d 348, a handler deployed a K9 on a fifteen-foot lead to track a teenage boy who had been drinking, had wandered off into the night, and who was believed to be in need of medical assistance. K9 tracked into a yard, into a bush and out of the view of the handler. After the lead went slack, the handler realized that K9 had located the boy and was biting the boy’s leg. The handler decided to physically pull K9 away from the boy rather than verbally call K9 off because the boy was struggling and the handler feared that if he performed a verbal call off, K9 would release and then bite the boy in the face. The boy’s father filed suit, alleging that the handler used excessive force in seizing the boy. The Fourth Circuit, finding that, although there were questions of fact as to whether excessive force was used, the handler was entitled to qualified immunity and the lawsuit was dismissed.

The fact that this case hinged on qualified immunity is not an open door to apprehend juveniles with a K9. Qualified immunity applied in this case because this issue was a novel one (meaning the courts could not find precedent that matched the facts here). Now that this case exists, the court will move on to the Graham v. Connor analysis to determine if an excessive use of force occurred.  This case might have had a different outcome in this situation.