And can poison hemlock cross pollinate with queen anne's lace? Would it produce potentially poisonous offsprings?

See if the identification guide, linked below, helps. The article was written for Australian weeds, but seems to apply to plants here, too. The "plants of similar appearance" section, toward the bottom of the article, may be of particular interest. If Poison Hemlock produces hybrids, it isn't well documented on the Internet.

Conium maculatum

thx. it says crrushed leaves give a mousey smell. So i can assume hemlock is safe to handle & smell then?

Edit: The website lists ground elder, fennel & queen anne's lace as the look alikes. I know what ground elder & queen anne's lace' leaves look like. So its not the 3 of them...

There are a good number of plants in the carrot family (Apiaceae) that look very similar so I understand your concern and confusion. This website may help but it doesn't include some of the more commonly encountered members of this family, like Anthriscus, angelica or sweet cicely.

Pretty sure it can't cross with others in the same family.