The argument that fentanyl played any significant role shows a profound lack of understanding of the mechanism of action of opiates (and to your point about the ME, if you read the article, it appears he was asked if both toxicology and heart disease contributed, rather than separating the two factors and asking individually, but that is more of a technicality).

To begin, let me state the obvious. Opiates have the potential to be incredibly dangerous. When improperly used, they can easily be deadly. But understanding how they are deadly shows why arguing that fentanyl (and of all opiates, especially fentanyl, more on that in a minute) played a significant role in this particular case is pretty, excuse my lack of a better term here, ignorant.

You see, as anyone who treats opiate overdoses knows, opiates generally kill through respiratory depressions. Individuals who overdose on opiates develop bradypnea (their respiratory rate slows), and as a result they become hypoxic (their oxygen level drops) and hypercarbic (their CO2 levels rise). In a typical person who has not overdosed on opiates, these conditions would trigger significant air hunger. Imagine trying to hold your breath for as long as possible, at some point your respiratory drive will overpower your sheer will and you will breath. But opiates suppress this respiratory drive, they suppress your air hunger. It is actually for this reason (more than pain control) that opiates are a mainstay in palliative/hospice/end of life care, because they can reduce the significant air hunger that some dying patients may experience.

As a brief aside before I conclude, I want to mention why the fact that it was Fentanyl, and not another opiate, is potentially important. You see, Fentanyl is among the fastest acting opiates. Relatively speaking, it's fast on, fast off. The effects are so rapid that it is a mainstay in many trauma bays across the country (more so than morphine, Dilaudid, etc). So if a massive Fentanyl overdose were the driving, or even a significant factor, in the death, the significant respiratory depression and reduction of air hunger should have been pretty obvious.

So how does all of this apply to the case at hand? Simple. If opiates played a significant role in the death of a patient, they should not demonstrate significant air hunger. They should not be screaming that they can't breath. I have long ago lost count of the opiate overdoses I have treated, not one has complained of difficulty breathing at the time of treatment (although there is a little known side effect of Narcan, thought to possibly be dose dependent, that can lead to pulmonary edema and dyspnea, although that's an entirely different tangent). If anything, the fact that he had fentanyl on board and was still screaming that he couldn't breath should further demonstrate the sheer brutality of the situation.

Now back to the testimony. Again, according to the linked article, the ME was asked if both the underlying conditions and toxicology likely contributed. Without commenting too much on the case, I would argue this is somewhat of an unfair question, as it groups two relatively unrelated things together. And specific to opiates, as I said they can lead to hypoxia, hypercarbia, etc, the same conditions caused by asphyxiation, so it is difficult to definitively say that they could not have contributed. When you consider the conditions of the case, however, I would argue that it is pretty ridiculous to suggest that fentanyl had any meaningful impact in the death.