The 38-year-old member of the British royal family and about 100 others are suing Mirror Group Newspapers (MGN), the publisher of the Daily Mirror, Sunday Mirror and Sunday People, over allegations of phone-hacking and unlawful information gathering between 1991 and 2011.
They claim senior editors and executives at MGN knew about and approved of the wrongdoing. MGN, owned by Reach, is fighting the lawsuit and says there is no evidence for the accusations.
The claimants' lawyer, David Sherborne, told the court on Wednesday that the case against MGN was "inferential", stressing that phone-hacking and other unlawful information gathering was a covert practice.
But, he added, the court could find that Harry was a victim of phone-hacking because of the prevalence of the practice at MGN newspapers and the level of press interest in the prince.
"The newspapers regarded him as a prime target, perhaps one of the most prime targets, in the sense of royal stories drive newspaper sales," Sherborne said.
He argued the idea that MGN would not have "used every opportunity to obtain stories" about Harry was "plainly implausible".
'WILDLY OVERSTATED'
MGN has previously admitted its titles were involved in unlawful information gathering and has settled more than 600 claims, at a cost of about £105 million ($NZ218 million).
But the publisher says there is no evidence Harry's phone was hacked, arguing some of the personal information about the prince in stories cited during the case had come from, or with the consent of, senior Buckingham Palace aides.
MGN's lawyer Andrew Green said on Wednesday that the lawsuits brought by Harry and others were "wildly overstated" and allegations of phone-hacking were not supported by evidence.
He added that Harry's case that he was the victim of "systemic hacking" over a 16-year period was "entirely speculative and bears little relation to the evidence".
On Tuesday, Sherborne had argued that MGN's failure to call its former employees, such as former Daily Mirror editor Piers Morgan, to give evidence was a fatal blow to its defence.
Morgan has always denied any knowledge of or involvement in wrongdoing and said, after the trial started, that he would not "take lectures on privacy invasion from Prince Harry".
MGN says calling Morgan as a witness was "disproportionate and unnecessary" and that the accusations against him were irrelevant.
Harry, the Duke of Sussex, became the first senior royal to give evidence in court for 130 years when he appeared this month for a day-and-a-half of questioning in the witness box.
The fifth-in-line to the throne said he believed phone- hacking took place on an industrial scale at MGN's titles.
MGN's lawyer Green argued in court filings that Harry's "undoubtedly fair resentment about his treatment by British and international media" had motivated his legal action, which he said was part of his "campaign to 'reform' the British press".
At the start of the trial in May, MGN admitted that on one occasion a private investigator had been engaged to unlawfully gather evidence about Harry.
However, it said he should receive no more than £500 in damages for that incident.
The trial is due to conclude on Friday with a ruling not expected for several months.
Harry and wife Meghan, Duchess of Sussex, stepped down as working members of the royal family in 2020 and now live in Los Angeles with their two young children.
