Nicknamed "the Sherlock Holmes of Saskatchewan" for her deductive skills and public fame,[1] McGill influenced the development of forensic pathology in Canadian police work and was internationally noted for her expertise in the subject.

[4]: xix  In 1915, McGill completed her medical degree at the University of Manitoba, receiving the Hutchison Gold Medal for highest academic standing,[9][10] the Dean's Prize and an award for surgical knowledge.

[8] Earning the unofficial nickname "the Sherlock Holmes of Saskatchewan",[8][5] McGill gained a professional reputation as a skilled and meticulous criminologist,[9] and was fondly called "Doc" by members of the police force.

"[5] She was known for handling the sometimes gruesome nature of her work by maintaining a good sense of humour,[5] and was a formidable, no-nonsense witness in court cases.

[8] During her court testimonies, McGill sometimes encountered young Saskatchewan defense lawyer John Diefenbaker – who would later become Prime Minister of Canada – and the strong-willed pair often sparred verbally.

"[13] McGill was acknowledged for her "untiring" efforts and "excellent" service in annual reports by RCMP Commissioners James Howden MacBrien[14] and Stuart Taylor Wood.

[11]: 39 Volunteering hundreds of additional work hours on evenings and weekends, McGill assisted the RCMP in establishing their first official laboratory for forensic detection, which opened in 1937.

[11]: 127  The laboratory took over a substantial portion of McGill's forensic pathology workload,[16] and over the next several years she concentrated on other projects such as developing a polio serum and becoming a specialist in allergy research.

She coped with the growing demands on her time by hiring an assistant and opening a private after-hours allergy clinic located at her apartment.

[11]: 129–131 McGill retired from her job as provincial pathologist on November 17, 1942,[17] having conducted more than 64,000 laboratory examinations over the course of her civil service career.

Several months afterwards, McGill decided to start a new project providing vaccinations for preschool children, and subsequently set up inoculation clinics at schools across Regina.

[19]: 26 In her new role as director, McGill conducted investigations across Saskatchewan[5] and provided lectures and training in pathology and toxicology to new police officers and detectives, teaching skills related to identifying blood samples, studying crime scenes, and properly collecting and preserving evidence.

She continued to work for the RCMP on a special consulting basis, and occasionally gave lectures and exams for police officers and investigators.

Police found bloodstains all across the room – presumed evidence of a violent struggle – and also located a rifle hidden in a nearby wheat bin.

The local doctor deemed it suspicious and ruled out suicide, and police arrested a neighbour who had been unable to satisfactorily explain several bloodstains on his coat.

[12]: 204  Although the previous doctor had decided that the victim must have died instantaneously, McGill found evidence in Shewchuck's digestion system that proved he had lived long enough to move around his house and hide the rifle, obscuring cause of death.

[19]: 28–29  The Lintlaw Case had a strong impact on McGill's reputation with police, and the RCMP subsequently made it their policy to call her in immediately whenever foul play was suspected.

Her work, revealing the bullet's clear trajectory and black lead markings,[19]: 28  showed that Schwab had been shot in the back of the head while sleeping.

"[23] During a period of cold weather, a hitchhiker was found frozen to death in a southern Saskatchewan field near South Poplar, his skull apparently fractured by a blow to the head.

[12]: 205  A truck driver admitted to drinking some alcohol with the hitchhiker, which had increased blood flow to the man's brain – and after his death, the below-freezing temperatures and position of the body had caused those fluids to expand, resulting in the apparent skull fracture.

From 1931 to 1933, her nephew Edward came to live with her in Regina while he built up his savings for university education, and he later cited her guidance and advice as a major influence on his life.

[11]: 160 She enjoyed travelling abroad and did so extensively, visiting New Zealand, Australia, South Africa, Mexico, the West Indies and multiple European countries.