Of the 33 men listed as serving with Canadian units in the WO 90 Courts Martial database at https://www.amymilnesmith.com/court-martial-records four received sentences of 10 years penal servitude. Two, serving with the Canadian Mounted Rifles in South Africa, were convicted of assisting the enemy on 13 June 1900.
The service file for Private W Pearce for the South African War at Library and Archives Canada gives his name as William, age 20 years and 1 month on enlistment on 28 Dec 1899, birthplace Bristol, England, father S. Pearce and mother S. Pearce.
A ship passenger list for the SS Dominion for May 1888 shows the family of Stephen Pearce (39) and Sarah Pearce (39) with children Henry (20), Emma (18), Thomas (14), Alfred (12), William (9), Stephen (4), and James (1). There’s a marriage record for Stephen Pearce and Sarah Ann Bentley in the September quarter of 1867 in Pewsey district.
Although the 10-year sentence was handed down in June 1900 he was soon free. In 1903 in Toronto there was a marriage of William Pearce, age 22, son of Stephen and Sarah, to Ina Jamieson. On 13 April 1904, William Walter Pearce was born in York Region to William and Ina. In the 1911 census William, age 7, is listed as a border with Alfred, likely his uncle.
The 1910 US census for Clayton, Genesee County, Michigan offers a tempting looking later record for William and his wife Ida. William Pearce, age 30, born Canada, a farm manager went to the US in 1908, followed a year later by his wife Ina (28), son Joseph (9) and Lillian (1), both born in Canada.
Any other suggestions for his later life?