The most widely publicized death of one of the Scientology organization's members involved the 1995 death of 36-year-old Lisa McPherson, while in the care of scientologists at the Scientology-owned Fort Harrison Hotel, in Clearwater, Florida. Despite McPherson's having experienced symptoms usually associated with mental illness (such as removing all of her clothes at the scene of a minor traffic accident), the Church intervened to prevent McPherson from receiving psychiatric treatment, and to return her to the custody of the Church of Scientology. Records show that she was then placed in isolation as part of a Scientology program known as the Introspection Rundown. Weeks later when it finally became clear that Lisa needed hospital admission they bypassed three nearer hospitals and took her to a distand hospital where a Scientologist was on duty.  She was pronounced dead on arrival at a hospital. The autopsy identified multiple hematomas (bruises), an abrasion on the nose and lesions consistent with "insect/animal bites" in the right lower arm just above the wrist.
Only Scientologists know what actually happened to Lisa though something has been leaked. We know from a description of Introspective Rundown that she could have been alone with auditors talking to her rarely while everyone else had to keep quiet. That's not likely to improve anybody's psychological condition. Lisa was described as emaciated here which suggests she didn’t get enough to eat either. The Lisa McPherson autopsy report states that cockroaches had been biting her while this website suggests she was still alive when at least some of the cockroach bites happened. There is even a suggestion that Scientologists intentionally killed Lisa or allowed her to die, see End of Cycle which is Scientology speak for intentionally causing or allowing someone to die. By contrast Death in slow motion: Part 2 of 3 in a special report on the Church of Scientology suggests that Scientologists were talking to Lisa but did other very bad things like holding her nose closed so she had to open her mouth to breath to try and force her to take medicine. I got from a report by five doctors that Lisa was severely dehydrated when she died also I got the symptoms of dehydration including severe dehydration from Effects of Dehydration, an impartial medical website. A report by five doctors states that she was severely dehydrated when she died. Scientologists even disagreed about when she died. 
Criminal charges were filed against the Church of Scientology by Florida authorities. The Church of Scientology denied any responsibility for McPherson's death and they vigorously contested the charges; the prosecuting attorneys ultimately dropped the criminal case and it is suspected this was due to Scientology pressure. After four years, a $100 million civil lawsuit filed by Lisa McPherson's family was settled in 2004. The terms of the settlement were sealed by the court.
Copied partly from here where I wrote part.