The regime of Syrian president Bashar al Assad deliberately targeted a building used by journalists during the siege of Homs in 2012, resulting in the deaths of reporter Marie Colvin and photographer Remi Ochlik, according to a landmark legal case brought by the Colvin family.

A cache of evidence compiled over the six years since Ms Colvin's death has been presented in court, including video from her final moments, nearly 200 confidential military documents and testimony from a Syrian defector.

The investigation alleges that the Syrian government tracked the American journalist’s movements in order to silence her reporting on the civil war. The plaintiffs are suing the Syrian government for $300m and calling on the federal court in Washington DC to issue a public judgement against the Assad regime, condemning it for its alleged crimes.

Speaking to The Independent, Ms Colvin's sister Cat Colvin said the Center for Justice and Accountability (CJA) had put together “a really powerful package of evidence”. “It has been emotional to read it,” she said.

“The case shows there was a well-planned effort to target journalists above everyone else in Syria: journalists, then the people leading rallies, then normal participants. It’s just horrifying,” she said, adding: “Marie deserved the truth.”

Scenes of devastation in Syria after deadly shelling and airstrikes and eastern Ghouta

Marie Colvin, a veteran foreign reporter for The Sunday Times, was on assignment with award-winning French photographer Remi Ochlik in February 2012, documenting the first major siege of the bloody war.

Rocket fire on the house they were staying in Homs’ Baba Amr neighbourhood killed them both and also injured British photographer Paul Conroy, French reporter Edith Bouvier and Syrian interpreter Wael al Omar. At least nine other civilians died in the bombardment.

The lawsuit included as evidence 10 eyewitness accounts of the attack as well as dozens of pages of Syrian intelligence and military documents and faxes which were smuggled out of the country by opposition activist group the Commission for International Justice and Accountability (CJA).

Inside Syria's obliterated ‘capital of the revolution’ Show all 10 1 /10 Inside Syria's obliterated ‘capital of the revolution’ Inside Syria's obliterated ‘capital of the revolution’ The reconstructed Khaled Bin al-Waleed Mosque is framed by a damaged building, in the old city of Homs AP Inside Syria's obliterated ‘capital of the revolution’ Sumaya Bairuty, 38, an English-language teacher who works in the capital Damascus, speaks with The Associated Press while as she walks to her parents house in the war-damaged Bab Dreib neighborhood of Homs AP Inside Syria's obliterated ‘capital of the revolution’ Bairuty walks to her parents house AP Inside Syria's obliterated ‘capital of the revolution’ A family that returned to live in their apartment inside a heavily damaged building hang their carpets in the sun AP Inside Syria's obliterated ‘capital of the revolution’ A car drives through a devastated part of the old city AP Inside Syria's obliterated ‘capital of the revolution’ A pigeon keeper watches his pigeons fly from the roof of his home AP Inside Syria's obliterated ‘capital of the revolution’ Two people carry goods on a bicycle in the war-damaged neighborhood AP Inside Syria's obliterated ‘capital of the revolution’ Children play football in the street AP Inside Syria's obliterated ‘capital of the revolution’ It has been almost four years since the last rebels and civilians withdrew from the remaining strongholds in the ancient heart of Homs in Syria AP Inside Syria's obliterated ‘capital of the revolution’ A man rides his bicycle past a banner showing Syrian President Bashar al-Assad AP

Lawyers for Ms Colvin’s family argue that an August 2011 fax, allegedly sent from Syria’s National Security Bureau, instructed security bodies to launch military and intelligence campaigns against “those who tarnish the image of Syria in foreign media and international organisations”.

Other documents showed that the Central Crisis Management Cell, a special war cabinet created by Assad to oversee the crackdown on the democratic opposition, had tracked Ms Colvin’s movements from Lebanon and over the border into Syria – evidence which the family's lawyers say showed she had been targeted for assassination by the highest levels of government.

The Syrian army’s Fourth Armoured Division, led by President Assad’s brother Maher, tracked Ms Colvin’s position by tracing her satellite phone signal and confirmed it through informants on the ground, according to the plaintiffs.

They allege that the house being used as a makeshift media centre to document the starvation and shelling of the siege of rebel-held Homs was then shelled by the Syrian Republican Guard and Special Forces working with a paramilitary death squad known as the shabiha.

President Assad has refused to acknowledge the US case. In his only public response in an interview in 2016 after the suit was filed, he said that Ms Colvin was responsible for her own death.

“It's a war and she came illegally to Syria, she worked with the terrorists and because she came illegally, she’s responsible for everything that befell her,” he said at the time.

Foreign governments are usually immune from US civil lawsuits, but there are exceptions for countries designated by the State Department as sponsors of terrorism, such as Syria.

The case, which is the first of its kind in the US brought against the Syrian government, should form a blueprint for other attempts at justice in Syria’s brutal war, said CJA attorney Scott Gilmore, who is representing Ms Colvin's family.

“This is a civil case seeking punitive and monetary damages of $300m, but that is not its primary goal – the primary goal is to establish a historical record of Syria’s horrors and galvanise and build support for other legal challenges around the world,” he told The Independent.

There are few avenues open for Syrians seeking justice against the alleged disappearances, torture and other crimes of the Syrian government. Last year, the head of the UN’s investigative panel into human rights abuses in the civil war resigned from her position because she was so frustrated with its inability to hold criminals to account.

Syrians make fuel from plastic waste Show all 8 1 /8 Syrians make fuel from plastic waste Syrians make fuel from plastic waste Sifting through plastic: the workshop uses plastic from bottles and other waste materials to produce liquid and gas fuels. The liquid is refined into gasoline, diesel and benzene fuels, which in turn are sold for domestic and commercial use Reuters Syrians make fuel from plastic waste Khodor, 20, at the workshop in the rebel-held and besieged neighbourhood of Douma, Damascus Reuters Syrians make fuel from plastic waste Back to basics: a man checks the heat of a pipe pouring with fuel Reuters Syrians make fuel from plastic waste Khodor, 20, must keep an eye on the burning plastic inside the workshop in Douma Reuters Syrians make fuel from plastic waste A young man takes a container of the locally made fuel, which can be used for domestic heating and on farms and bakeries Reuters Syrians make fuel from plastic waste Abu Fahad on a rest break with his colleagues inside the workshop, where the air is heavy with toxic fumes Reuters Syrians make fuel from plastic waste Fuel drips into a container at the workshop. Most locals are glad of the family-run business, which has restored a degree of normality to the region Reuters Syrians make fuel from plastic waste Khodor extracts fuel from plastic in the workshop Reuters

“There are multiple criminal inquiries ongoing using the principles of universal jurisdiction. But in the absence of any functioning UN mechanisms for Syrian war crimes, seeking truth and justice is a very difficult challenge,” Mr Gilmore said.

“Our family feels great solidarity with the Syrian people,” Cat Colvin said.

“It’s so painful to think this tragedy is still ongoing and no one seems to care anymore. Witnesses risked their lives to get us this evidence. We are eternally grateful.

“Marie’s legacy is drawing attention to these issues. Her work and voice continue.”