Ryan Passey died after being knifed in Chicago's in 2017. Kobe Murray was later cleared by a jury. He admitted stabbing Mr Passey but said he did so in self-defence.
Mr Passey's family launched civil proceedings against Mr Murray in December last year in the hope of securing public recognition that 24-year-old Mr Passey was unlawfully killed, after being left devastated by the jury's decision.
Now, after Mr Murray failed to file a defence to the civil proceedings by the agreed deadline, the family have decided to apply to a court for a default judgement to be made.
A default judgement means judgement without trial where a defendant has failed an Acknowledgement of Service or has failed to file a defence.
The family received an Acknowledgement of Service from Mr Murray's solicitor on December 15, with a 28-day extension agreed to acquire the original files which fell on January 27.
A final extension was granted on January 19 to allow for Mr Murray's defence to be filed by February 25.
Mr Murray, who, according to the Passey campaign, has split from his solicitors, was due to file his defence by that date.
However no further contact has been made to the family, or the Justice for Ryan campaign, regarding the defence which has led to them applying for the default judgement to be made against Mr Murray.
A spokesman from the campaign said: "We will now be moving forwards and instructing our legal team to write to the courts to request an application for a default judgment to be made against him, legally holding him responsible for the unlawful killing of Ryan.
"This is just one of a number of actions we are currently undertaking in our fight to get Justice for Ryan."