Born in Washington, D.C., Edmonston served as a United States Army infantry medic in Panama from 1961 to 1964, where he witnessed the so-called flag riots,[3] and graduated from the Canal Zone College.
Edmonston has served as a pro bono witness on automobile defects and safety before numerous courts and government committees.
In 1982, he testified on inadequate automobile quality and rust protection before the United States Senate Subcommittee on Technology and successfully pressured Ford to become the first automaker to provide a corrosion compensation warranty.
[2] Edmonston entered Canadian politics in the 1988 federal election as a candidate for the New Democratic Party (NDP) in Chambly, Quebec, placing second.
Edmonston's differences with the NDP over its position on Canadian federalism and against decentralization and devolving powers to Quebec contributed to his decision not to run for re-election in 1993.