11/01/2013 AT 05:30 PM EDT
11/01/2013 AT 01:15 PM EDT
A medical examiner testified he was unable to prove how the wife of a Utah doctor charged with murder
died, possibly complicating an eventual decision by jurors in the case.
The witness, Todd Grey, said Thursday that Michele MacNeill's heart may have stopped beating because of a combination of heart disease and drug toxicity, and that it was possible the 50-year-old woman drowned in a bathtub where she was found.
"I didn't believe I had enough to justify homicide," Grey testified about his finding in the case involving defendant Martin MacNeill.
Grey said an irregular heartbeat was the most probable manner of death, but he doesn't know what caused it. A heart arrhythmia "leaves no footprints" that can be detected by a forensic pathologist, he said.
However, when asked by the prosecutor if it was hypothetically possible if someone "drugged up Michele and convinced her to get into the tub, and held her down for a little bit [to drown her]," he replied: "Yes, it certainly is possible."
Grey's testimony came a day after a second mistress
of Martin MacNeill, 57, testified that the doctor once described during pillow talk how he could induce a heart attack in someone that would appear natural.
Prosecutors have alleged that MacNeill hounded his wife to get cosmetic surgery, then knocked her out with painkillers, Valium and sleeping pills and drowned her in the bathtub.
Defense lawyers have argued Michele had a heart attack while her husband was at work.
The trial is expected to last through mid-November.