The judge was clear: it was murder. The Sunday Times correspondent Marie Colvin, killed while reporting from the besieged Syrian enclave of Baba Amr in February 2012, was not the victim of a tragic accident.

“She was specifically targeted because of her profession, for the purpose of silencing those reporting on the growing opposition movement in the country,” wrote Judge Amy Berman Jackson of the US District Court in Washington DC.

Her verdict should be celebrated by all who care about freedom of speech. At a time when journalists are frequently vilified and threatened, it acknowledges the significant role we play in exposing war crimes and injustice. “The murder of journalists acting in their professional capacity could have a chilling effect on reporting such events worldwide,” Jackson added.

I will never forget my last conversation with Marie, who was speaking on Skype from Baba Amr in Homs. President Bashar al-Assad had said only terrorists remained there, but she told me about the injured children she had seen cowering under the terrifying, relentless bombardment by the Fourth Armoured Division of the Syrian army. Marie and I had reported from many war zones, but I had never heard her sound so desperate. She said: “Lindsey, this is the worst we’ve ever seen.”

A few hours later, Marie and a French photographer, Rémi Ochlik, were killed in an artillery barrage. The photographer Paul Conroy, a former British soldier who was badly injured in the attack, has described how the makeshift media centre where they were staying was “bracketed” – a technique for centring on a target.

The feature film and documentary that have been made about Marie and the biography I wrote are testament to her extraordinary life, but this judgment gives meaning to her death at the age of 56.

“It won’t bring Marie back but it will hold someone accountable,” said her sister, Cathleen Colvin, who brought the case. “I hope it sends a message to the world about the targeting of journalists.”

This was a civil not a criminal case, as Syria is not a signatory to the Rome Statute enforced by the International Criminal Court in The Hague, and President Bashar al-Assad’s protector, Russia, has vetoed any attempt to set up a special tribunal. US law allows prosecution if the accused state is deemed a sponsor of terrorism. The judge awarded punitive damages of more than $300m to Cathleen Colvin, not just because she and her children would be deprived of a beloved sister and aunt but because “a targeted murder of an American citizen whose courageous work was not only important, but vital to our understanding of war zones and of wars generally, is outrageous”.

A parallel case has been launched in France on behalf of the family of Rémi Ochlik and also Edith Bouvier, a reporter for Le Figaro who was injured in the attack.

The Colvin family is unlikely to see their money, although they may pursue frozen Syrian assets, but they hope that a precedent has been set for Syrian civilians. The lead counsel, Scott Gilmore of the Centre for Justice and Accountability, said: “We’re really hoping this case will send a powerful signal that there will be justice for perpetrators of war crimes in Syria.”

Compelling testimony came from a defector codenamed Ulysses, who described how the Syrian military intercepted Colvin’s broadcasts to CNN, the BBC and Channel 4 News, paid an informer to confirm where the journalists were staying and celebrated her death. Since the war in Syria began, other defectors have smuggled out millions of documents that implicate the regime in countless crimes against humanity. Cases are now under way in Germany and France on behalf of Syrian refugees who were tortured in Assad’s prisons or whose relatives were “disappeared”.

These days the danger to journalists is not restricted to those reporting from war zones or rogue regimes – three journalists have been killed in the European Union in the past 18 months. Investigating the nexus between organised crime and corrupt officials is especially perilous. The commitment of Malta to establish who killed Daphne Caruana Galizia, blown up by a car bomb in October 2017, may be undermined by the Maltese prime minister Joseph Muscat, who even last week was in court pursuing a libel case against her.

Judge Jackson noted that the Syrian government regarded journalists as “enemies of the state”. Her court lies just 10 minutes drive from the White House, where the US president frequently calls journalists “enemies of the people”. I wonder if that will be on her mind as she deals with the next cases she has been assigned – charges against the men who allegedly used the dark arts of media manipulation to get President Trump elected: his former campaign chairman Paul Manafort and adviser Roger Stone.

Lindsey Hilsum is international editor for Channel 4 News, and the author of In Extremis: the Life of War Correspondent Marie Colvin (Chatto and Windus, 2018)