[jerf]

Depends on your personal tolerance for the complexity indicated by the word "chemical". The presence of "deoxyribonucleic acid" on its own does not prove life, as that term covers simple cases of it that could conceivably naturally occur. However, if you've got a multi-million base pair chain of the stuff, wrapped up in chromatin, and bespeckled with all manner of useful-looking biochemical doohickeys attached to it, I'm willing to say that's definitely indicative of life. Is that a "chemical"? I'd certainly call that a "molecule" that could only be produced by life.