"Máte na rukách jeho krev" it is also the right answer. Lokativ pl. animate form are possible both forms rukách/rukou.
Máš na svých rukou jeho krev. It's more natural.
It isn't. But it is possible.
But foremost, the English sentence is a translation of the Czech one, not the other way.
Why "Mate jeho krev na rukou" is not correct?
It is, mostly for the literal meaning though. Added this and a bunch of other options.