So where should the line be drawn for using DNA analysis to resolve crimes? I mean how serious should crimes be before DNA analysis should be allowed? Murder, I

So where should the line be drawn for using DNA analysis to resolve crimes? I mean how serious should crimes be before DNA analysis should be allowed? Murder, I suppose - but why not dog poo? Living in the German city with the highest density of dogs in the country, I find dog poo highly annoying. It completely spoils the parks, for example.