Jessie McTavish began her nursing career at Ruchill Hospital in Glasgow, Scotland. She worked in Ward 5, where she was responsible for the care of numerous patients. Her colleagues initially regarded her as a dedicated and competent nurse.

In 1974, McTavish was charged with the murder of 80-year-old patient Elizabeth Lyon by administering a lethal dose of insulin. She was also accused of assaulting three other patients by giving them unauthorized injections. During the trial, colleagues testified that McTavish had administered unnecessary doses of medications without proper documentation, and she had allegedly remarked, "Doctor likes them to go quietly." Despite her defense claiming she had only administered placebos, McTavish was convicted and sentenced to life imprisonment in October 1974.

However, in February 1975, her conviction was overturned on appeal. The appellate judges acknowledged that while there was sufficient evidence to support the original conviction, the trial judge had inadvertently misled the jury by not highlighting McTavish's denial of admitting to the police that she had committed a mercy killing. This oversight led to her release.

Following her release, McTavish married and became Jessie Gordon in 1976. In 1984, she was reinstated to the professional register for nursing, midwifery, and health visiting, allowing her to resume her nursing career. Her case has been cited in medical and forensic discussions, particularly concerning the misuse of insulin as a method for committing undetectable murders. Notably, her case was discussed in lectures attended by Colin Norris, a nurse later convicted of murdering patients using insulin, suggesting her case may have influenced his actions.