Me and a buddy and his father learned a hard lesson with turtle years ago. I'll never forget it: my buddy's dad wanted to make snapping turtle one time. So he put all kinds of work into this soup, but while he was cooking it me and his son kept telling him that it didn't smell right to us.
His dad just kept telling us that is was because we didn't know what was good...so finally dinner time rolls around and he starts dishing it out.
My buddy came up with what I thought was a good idea; he called their black lab in and put a small amount in her bowl. She wouldn't touch it! Even with some encouragement, she wouldn't go near it. So we (as respectfully as we could) declined and told him we were not going to eat it. (Looking back, I'm thankful we were in our late teens at the time, because if we were younger, he'd have made us eat it...) Of course he was ticked at us and probably, just out of wanting to prove a point to us - he went ahead and ate it.
About 6 hours later, we rushed him to the hospital and they pumped his stomach! Ever since then, I've always trusted my sense of smell.