Detective Inspector Kenneth McAndrew, 37, told the High Court in Glasgow he was informed of a fire at the Venus Hair and Beauty Salon in Stirling's Maxwell Place on October 12 last year and went to the location.
He said by the time he arrived two people had been taken away by ambulance. He said 12 pieces of card with writing on them and a lighter were found.
Mr McAndrew said one card read: "If she was in Iran she wasn't doing that to me and my children. Game is over." Another referred to her fasting and reading the Koran but said she was "doing adultery".
Mr McAndrew was giving evidence at the trial of Ahmad Yazdanparast, 61, who denies murdering his ex-wife Ahdieh Khayatzadeh or Yazdanparast, 46, at the hair salon where she worked.
Yazdanparast has lodged a special defence maintaining he acted in self-defence. The trial continues.