The widow of a policeman slain the Jeppestown shootout shook her head in disbelief on Tuesday when a robber's counsel asked the Johannesburg High Court for mercy when passing sentence.

Inspector Leonie van Heerden sat listening when Senzo Emmanuel Mweli's advocate asked judge Ratha Mokgoatlheng to guard against destroying his client's young life.

Holding onto her slain husband's wedding band attached to a neckpiece, Van Heerden sat quietly in the court, constantly shaking her head as advocate Tumelo Ntshwane argued in mitigation of Mweli's sentencing.

Van Heerden's husband, Frederick Jacobus van Heerden was among the four police officers gunned down during a bloody shootout with armed robbers in Jeppestown two years ago.

"I submit these are serious charges... but sentencing should not be used to destroy the life of the accused. At 29 he is still young," Ntshwane told the court.

He said Mokgoatlheng should also consider the fact that Mweli has already spent two years behind bars.

Mweli was last week convicted on charges of aggravated robbery and attempted murder.

The judge had initially erred and convicted him on further charges of murder.

Although he rectified this mistake an hour later, this issue became a matter of contention during arguments on Tuesday morning.

Advocate Robin Stranscham-Ford, who was standing in for Ntshwane at the time, said Mokgoatlheng had acted unconstitutionally in convicting Mweli on charges he was never charged with.

"There were irregularities... the defence doesn't accept that this was a mistake, in so doing the judge pre-judged the matter. The judge went beyond convicting him and that is unacceptable," Stranscham-Ford said.

He said they would take the matter up with the appeals court after Judge Mokgoatlheng denied prejudicing Mweli and dismissed an application by the defence to have him acknowledge that on record.

This followed a special application by the defence to have Mokgoatlheng "enter on record irregularities made".

State advocate Leonie Spies was expected to start her argument in mitigation following a lunch break.

Sapa