Recognized as the leading Obstetrician, Gynaecologist and Paediatrician in Kingston, Lavell became Surgeon of the Kingston General Hospital and Surgeon with the Frontenac Militia. In 1866, he was one of the founders of the Royal College of Physicians and Surgeons in Kingston.

In 1872, Dr. Lavell was appointed Surgeon of Kingston Penitentiary. Believing in the medical education of women, who at the time couldn’t attend medical classes with men, Dr. Lavell helped to found the “Women’s Medical College” in Kingston. He served as the President, Dean and Professor of Obstetrics there from 1883 to 1885.

On February 3, 1885, Lavell became Warden of Kingston Penitentiary, a post he reluctantly accepted. He lived in Cedarhedge with his wife, Betsy, and their 10 children.

In 1885, Prime Minister Macdonald asked Dr. Lavell and Dr. Valade (of Montreal) to examine Louis Riel. Riel had been sentenced to death because of an uprising he had led in the West. The doctors were to determine whether Riel was “…so bereft of his reason as not to know right from wrong and as not to be an accountable being”. Dr. Lavell found that “Riel, although holding and expressing foolish & peculiar views as to religion and general government, is an accountable being and capable of distinguishing right from wrong”. As a result, the sentence of death was carried out. Dr. Lavell himself died in Kingston in 1901.