Police chiefs are seeking to overturn a legal ruling won by an 89-year-old campaigner whose political activities were recorded on a clandestine database.

On Tuesday, lawyers for the police argued at the supreme court that a secretive police unit that says it tracks domestic extremists acted lawfully when it monitored John Catt, who has no criminal record.

Catt has said he was “shocked and terrified” when he discovered that police had logged details of his presence 66 times at peace and human rights demonstrations over a four-year period.

The police had recorded how the Brighton campaigner turned up at the demonstrations and sketched the scene. They also documented the clothes he was wearing, his appearance, such as “clean-shaven”, and the vehicle he was driving.

The ruling, to be delivered by the five supreme court judges, is expected to help determine how far the police can monitor and store details of the activities of political campaigners in their files.

The Metropolitan police have faced criticism following revelations that their domestic extremism unit gathered information about law-abiding campaigners. The unit has been keeping files on thousands of people, including Jenny Jones, the Green party’s sole peer, and journalists. It also recorded how an activist sold anti-capitalist publications at the Glastonbury music festival.

Police argue that they need to keep tabs on many activists to identify the ones who are willing to commit crime to achieve their political aims.

Catt launched his legal case three years ago after using the data protection act to obtain the file on his political activities between 2005 and 2009 that had been created by the police’s domestic extremism unit.

One entry recorded that Catt “was using his drawing pad to sketch a picture of the protest and police presence”. Another read: “John Catt sat on a folding chair ... and appeared to be sketching.”

Police continued recording Catt’s political activities after he started legal action to get his file destroyed. One of the reports recorded that he attended a demonstration against government spending cuts in Brighton in June 2011.

Catt, who volunteered to fight in the second world war at the age of 17, has campaigned for peace and human rights for several decades. He has told judges that he is “committed to protesting through entirely peaceful means”.

At the opening of the three-day hearing, Jeremy Johnson, QC for the police, told the court that the entries about Catt were “used by the police for intelligence purposes – broadly to learn the tactics used by protest groups that engage in criminality and to determine the appropriate response to such protests”.

He added: “The demonstrations were marked by violence such that a policing response was necessary to order to prevent disorder, facilitate peaceful protest and protect the rights of others.”

He argued that the pensioner’s privacy had not been violated as he “was taking part in public protests, positively and publicly seeking to demonstrate his support.”

He said the number of records kept about Catt were “far fewer” as the police reviewed their files to see if they were still needed. The police are challenging a ruling by three judges in the court of appeal who ordered the deletion of Catt’s file from the domestic extremism database. The appeal judges said police could not explain why it was necessary to record Catt’s political activities in detail.

Catt’s case is being supported at the hearing by Network for Police Monitoring, a civil liberties group. Its co-ordinator, Kevin Blowe, said: “The outcome of this hearing is extremely important, because a victory for the Metropolitan police will make it significantly easier for intelligence-gathering officers to continue to obtain and retain data about protesters on an almost industrial scale.”