Keeping a connection between two rigs in place

Just wondering if there is an easy solution to a regular animation problem. Here is a hypothetical example to illustrate the problem. A cop escorts a prisoner to his car keeping a hand on the shoulder of the man in cuffs. This can be done with two rigs with walk cycles. The difficulty is the hand on the shoulder. Is there a way of making the cops hand follow the shoulder of his ward, so his hand does not slip. Would parenting an empty to the shoulder bone and then adding a “child of” bone constraint to the hand work? Doesn’t seem too for me perhaps I’m missing something. Would a hook work?

Basically, yes.

Child-of acts after parenting relationships and keyframes. So the hand would have to be unparented and unanimated for it to work properly, without slipping.

In practice, this is generally done not by child-of’ing the hand directly to the empty, but by child-of’ing an IK target to the shoulder (and, probably, copying rotation world->world from IK target to hand.) IK targets are not generally parented. If you’re doing object-level animation, however, you wouldn’t want an IK target inside that armature; you’d probably just use the empty as the IK target, since it doesn’t exist inside the armature object.

And, of course, if the arm couldn’t reach the IK target, the hand would slip rather than become disconnected from the arm.

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Thank you for the reply. Lots of useful information. It’s good to know I was on the right track I’ll do a few more experiments to see if I can perfect a technique.