"I had to do it with my own parents"
Just the odds, but making both parents die by starvation and dehydration is extremely rare and questionable.
I've seen hundreds of elderly patients, and have seen one or two neglected and starved to death, and nurses not allowed around, sent home. Guardians/family used to murder them under the guise of a pain killer, a morpheine drip, which is actually too strong for the body, which causes the body to shut down. Usually a weak body dies on its own, pneumonia, or heart.
But for Michael to do this to both parents sounds very suspicious.
Morphine for terminal cancer patients on their way out is one thing. It's purpose is to kill pain, and sometimes it hastens death as a byproduct. My grandpa had morphine for the colon cancer that killed him, as do most other terminal patients. My father in law died two weeks ago of oat-cell lung cancer (which has the worst prognosis of any lung disease, incl. other forms of lung cancer except mesothelioma, which is really a pleural disease, not lung); he had morphine, and finally just stopped breathing. Whether that came from the morphine or from the cancer growing into the mediastinal cavity and stopping the heart is debateable. Either way, he was in the final stages of a disease for which he had had no chemotherapy and which kills 94% of its victims.
I do not believe that counts as murder in the same way as dehydrating a disabled but otherwise healthy human being in her early 40's like Terri.