This image was created by Chris Ryann at the Centre for Anatomy and Human Identification in Dundee. It's based on his skull as well as descriptions in court papers.
Engraving or James McDermott and Grace Marks upon their trial at Toronto, Upper Canada, November 3RD AND 4TH, 1843. As they appeared at the Court House. Accused of Murdering Mr. Thos. Kinnear & Nancy Montgomery