Mr Cull was one of three new JPs to be sworn in at a ceremony at the Dunedin District Court, conducted by Family Court judge Mary O'Dwyer.
However, for the new mayor it was obligation rather than inspiration that resulted in him standing before the bench.
"All mayors become JPs and the warrant is withdrawn once they cease office," Otago Justices of the Peace Association president Russell Atkinson explained.
"We usually swear the mayor in at a private ceremony, but Dave was delighted to participate in this ceremony with the others. He will be an ex officio JP, but we hope he will keep up his membership in the future."
Being a justice of the peace was an "ancient and honourable role", Mr Atkinson said.
Also sworn in yesterday were Laura Black, of Dunedin, and Gary Johnson, of Palmerston.
The new JPs received a badge of office and certificate of membership.
The 200th anniversary of the first New Zealand justice of the peace, Thomas Kendall, will be commemorated in 2014.
