I think you may have misread that part. Mash isn't and wasn't the medical examiner ever that I can find online. As best I can piece this together from that article and some Googling, Taser hired Mash as an expert witness in 8 trials for a total of ~$24,000 (included just because I believe that's in the normal range for that kind of testimony).
Then Mark Shuman, who is an Associate Medical Examiner, sent brain tissue samples to Mash's lab without knowing that Taser had previously paid her for testimony.
That's not to say the situation or diagnosis is okay, just that I think this is accusing them of something that didn't happen. There's plenty of crap they have done to criticize them for.
That Wikipedia article would be funny if the situation wasn't so tragic. It's utterly unintelligible. A condition with no proposed cause, which causes death with no specified mechanism, and a list of symptoms that matches everything from "stressed out about being arrested", to a psychotic break, to "actively overdosing on PCP". How they ever manage to convince a jury that the cardiac arrest is from some vague syndrome and not the police having basically put nipple clamps connected to mains voltage on them is beyond me.