Dave graduated from the University of Toronto, Faculty of Law, and articled at Agro, Zaffiro in Hamilton before he was called to the Ontario Bar in 1976. Over the subsequent twelve years, he practised in the area of personal injury and insurance litigation at Agro, Zaffiro before forming his own firm, Dempster, Dermody & Riley where he continued his practice until 1999. During this time, Dave gained extensive trial experience and appeared at all levels of the Ontario court system.

In 1998, Dave received mediation training at the Center for Dispute Resolution in Boulder, Colorado. Since then, he has been mediating full-time with M + F Mediation and Arbitration Services. In fact, he has developed into one of the busiest mediators in the province, specializing in tort- and insurance-related claims.

Dave is a member of the Canadian Bar Association, the Advocates' Society, the Hamilton Law Association, the Medical-Legal Society of Hamilton and the Hamilton Lawyers' Club. As well, he is a past director of the Ontario Expropriation Association.