There is no such thing as an automatic lethal dose of Fentanyl or any other drug. Tolerance for users is normal. What may be a lethal dose for a first time user may not even give a serious addict a buzz. That is the point of addiction. Your body becomes accustomed to the drug and you require an increasing dose to get the same effect.
The same is true of anyone who uses any kind of physiological modification substance. It is why smoking your Grandpa’s cigar made you sick as a child, but doesn’t as an experienced adult.
That is the problem with the claim of lethal limit. So to determine if it was an overdose among other things the ME examines the heart and lungs to look for signs. He or She examines the nose and throat looking for signs.
It isn’t just a simple blood test and done.
Finally. Your frankly stupid assertion that if it was a different location the “expert” would be emboldened to tell the “truth”. The trial would still be televised and everyone would know who this expert is. So this imaginary threat would still exist wouldn’t it?
But your assertion is laughable before we get there. There are more than 3,000 counties. Assume st least half of them have Coroners who are experienced and respected. Add in any who are coroners for cities. You have to assume there are at least two thousand. Plus professors of forensic medicine and all that. So figure at least two thousand potential experts. And somehow, according to you, they are all cowards. Not one will tell the truth?