Lawyers for Duke and Duchess of Cambridge seek compensation of 1.5 million euros ($ 1.64 million) from the magazine Clauser, Mavable published a picture of bare-chested Middleton.
French prosecutors have asked a court to impose a heavy fine on the celebrity magazine, if it is found guilty of violating the privacy of the Duke of Cambridge, by publishing pictures of her in 2012.
The editor of the magazine, Lawrence Pew, and Ernesto Mori, chief executive of the Mondadore Italian publishing group, the owner of the magazine and two Paris agency photographers suspected of taking photographs, stood before a court hearing in Paris's Nanterre neighborhood to respond to accusations against them under French privacy laws.
The two photographers told the court that they had not picked up those pictures.
They said they had not been able to find the residence of the prince and his wife, while court documents indicated that the mobile phone records showed that the photographers were near the house at the time.
Britain's Press Press quoted William as saying in court that the decision to publish his wife's chestless photographs was "particularly shocking" given the battles of his late mother Diana with the curious photographers.