Since you don't indicate the units or the sample, I will assume the sample is blood and the units are the forensic standard, g/100ml.
This translates directly to a blood alcohol percent - 0.03%. The legal limit for driving in most (if not all) states is 0.08%. So, 0.03% is not going to kill anyone. That's at most about one standard drink's worth, give or take.
This level could very well represent postmortem production (by bacteria in the gut), depending on the PM interval, temperature, and some other things.