Double Jeopardy harsh law or joke?

Yeah, neither. It is a protection. Double Jeopardy protects one from being placed under threat of losing life or limb twice for the same offense. Of course, committing the same offense two separate times does not qualify under the right, one can still be tried civilly after being found not guilty criminally, and I believe one can be tried again if a mistrial is declared. So yes, not a harsh law at all as it is a Constitutional protection and certainly not a joke- especially if one finds him/herself in a relevant situation.