Seith has been a sheriff since 2003, now at Paisley Sheriff Court. His judicial work includes both criminal work and family work bringing him into contact with people whose lives have been affected by problems with alcohol and drug addiction. In his work in criminal cases he has supervised and made submissions to government and other bodies for improvement in court orders directed to assist offenders overcome drug and alcohol problems.
Prior to appointment to the Bench, he was a solicitor with his own practice. He has previously served on a number of University and Professional bodies including being President of the Glasgow Bar Association and serving on the Council of the Law Society of Scotland. He presently serves as a mentor to graduate students at the University of Glasgow and is on the Council of the Scottish Association for the Study of Offending (“SASO”).