Johnson holds a Bachelor of Laws degree, and her legal training led to admission to the bar in Scotland in 1979.
Solicitors in Scotland were once called writers, and the Writers to the Signet were part of the College of Justice established by James V in 1532. That body recognised judges and lawyers as separate from the state and remains the foundation of Scotland's legal system, so a Scottish legal career developed within a framework distinct from England's.
Johnson was admitted to the bar in Scotland in 1979, beginning a legal career within the Scottish profession. Her documented professional role is that of partner at Maclay Murray & Spens.
Maclay Murray & Spens was founded in Glasgow in 1871 by David Maclay, David Murray and John Spens, and it was the first law firm in Scotland with a specifically commercial practice. By the time of its merger it had offices in Aberdeen, Edinburgh, Glasgow and London, and it was one of the few remaining large independent Scottish firms. In July 2017 the firm announced it would join Dentons, then the largest law firm in the world by number of lawyers, and the combination was completed in October 2017 with the adoption of the Dentons brand.
Johnson also holds the office of notary public, a formal designation that accompanies her legal practice.
Johnson is a Writer to the Signet. The Society of Writers to Her Majesty's Signet, which meets at the Signet Library in Edinburgh, is a private society of Scottish solicitors whose origins date to 1594 and which forms part of the College of Justice. The society originally held special privileges over the drafting of documents requiring the signet, but it now operates as an independent, non-regulatory association of solicitors, and its members may use the post-nominal letters WS.
