Caoime McCann is seeking to judicially review an alleged failure to state whether the shot which claimed the life of 21-year-old Neil McConville was necessary.
Mr McConville was killed following a car chase at Glenavy, Co Antrim in April 2003.
Police mounted an operation to stop the Vauxhall Cavalier he had been driving due to suspicions that a firearm was being transported.
An officer opened fire three times amid fears Mr McConville was about to drive over a colleague knocked down at the scene.
The father of two died from a gunshot wound to the chest.
Earlier this month an inquest into his death reached a finding that the use of lethal force was justified.
However, the coroner also held that the police operation was not planned and controlled in a way that minimised the possible need for such force.
Lawyers for Mr McConville’s partner at the time of his death are now seeking to have the findings declared unlawful.
They allege a breach of human rights over failures by the coroner to set out conclusions on a number of disputed central factual issues.
A key area relates to the gun used to open fire on Mr McConville.
Ms McCann’s solicitor, Setanta Marley of KRW Law, confirmed judicial review proceedings have been filed at the High Court in Belfast.
He claimed police were aware of an issue with the weapon that would lead to more shots being discharged than intended.
“In this case, the officer intended to fire only one shot,” Mr Marley said.
“Despite this, the coroner failed to state his conclusions as to whether the firing of the second of the three shots fired, which was the fatal shot, was justified and/or absolutely necessary.
“For these reasons, my client seeks a declaration from the court that the coroner has breached his procedural obligations under Article 2 of the European Convention on Human Rights.”