Wilson was born JoAnn Geiger in Osage, Iowa to Harlan and Betty Geiger. She met Colin while attending Iowa State University in 1960, and in 1962 the couple married and relocated to Moose Jaw, Saskatchewan. While Colin was pursuing his political ambitions, JoAnn helped raise their three children and worked variously as a teacher, bookkeeper, and interior designer. The Thatcher marriage began to sour in the late 1970s, culminating in physical abuse and finally a divorce. Colin continued to abuse and harass JoAnn even after her marriage to Tony Wilson on 3 January1981. Two years after an unsuccessful attempt on her life in later that year, JoAnn was found beaten and shot to death in the garage of her Regina home. After a lengthy police investigation, Thatcher was charged and convicted of the murder.
Thatcher was convicted of first-degree murder in November 1984 and was sentenced to life in prison with no chance of parole for 25 years.
Thatcher is convicted of first-degree murder in the death of his ex-wife, JoAnn Wilson, and sentenced to life in prison with no chance of parole for 25 years.
Thatcher is re-elected to the Saskatchewan Legislative Assembly.