Prince's slap not a beating

Princess Caroline of Monaco told a court that her husband slapped a hotel owner in Kenya as a symbolic reproach over noise from a disco but did not beat the man.

Prince Ernst August of Hanover - a distant relative of Britain's Queen Elizabeth II - is being retried on charges of causing serious bodily harm in the 2000 incident.

The princess, clad in black, told the court in English that her husband "got angry" with Josef Brunlehner, owner of a hotel on Lamu Island, and slapped him twice with an open hand after becoming irritated at the noise from a disco.

"I would say it was not very strong. It was more symbolic," Caroline, 52, testified.

Ernst August, 55, great-grandson of the last German emperor, Wilhelm II - is being retried after being convicted in 2004 and fined 445,000 euros ($NZ872,000).

Ernst August does not deny the assault but he is seeking to have the charge and sentence reduced.

Caroline, 52, testified behind closed doors on her husband's behalf in a 2008 hearing that led to the retrial. She agreed to Wednesday's appearance after the court guaranteed that media and others would be kept at least three metres away from her.

In the first trial, the court ruled that Ernst August repeatedly hit Brunlehner with a metal ring that he was wearing in January 2000.

Ernst August said that he only slapped Brunlehner. Caroline added that her husband never wears rings - not even his wedding band.

Kenyan authorities did not arrest Ernst August after the incident, but it was pursued in Germany where the law allows prosecutors to charge citizens who commit crimes abroad.

It is not Ernst August's first run-in with the law; he was fined in 1999 for attacking a German photographer and had his driver's licence suspended for a month in 2003 for speeding on a French highway.

- AP