Two of the three teenagers jailed for killing PC Andrew Harper have launched appeals against their manslaughter convictions.
Albert Bowers and Jessie Cole, both 18, have lodged applications with the Court of Appeal seeking permission to challenge their convictions and their 13-year prison sentences.
No date has been set for the hearing of the appeals.
It came as PC Harper’s widow, Lissie Harper, launched a petition to show the level of public support for tougher jail terms for people who kill emergency services workers.
The 29-year-old is trying to secure a meeting with Home Secretary Priti Patel and wants to show the extent of the backing for her campaign.
Harper’s Law would see anyone convicted of killing an emergency services worker given a life sentence.
The 28-year-old Thames Valley police officer died trying to stop Bowers, Cole, and 19-year-old Henry Long from towing away a quad bike stolen from outside a house in Berkshire in August last year.
He was dragged for a mile behind their car, driven by Long, who was sentenced to 16 years in prison last month.
All three teenagers were cleared of murder. Long admitted manslaughter and his co-accused were found guilty of the same offence.
Sentencing judge Mr Justice Edis described the killers as “young, unintelligent but professional criminals”, and said none of them had “shown anything resembling remorse”.
Mrs Harper has said she was “utterly shocked and appalled” at the decision not to convict the trio of murder.
Bowers and Cole could be out on licence after serving less than nine years, under legislation that says a prisoner is eligible for release after serving two-thirds of their sentence.
Mrs Harper told Sky News: “I’ve learnt an awful lot this past year about grief and strength and trying to be brave, which brings me to why I’m doing this now.
“I want to make something out of this horrific year.
“Instead of Andrew’s legacy being about the horrible way he died maybe we can make a positive change I know he’d be proud of.
“A year, astonishingly, has passed and now I want to focus on this and I’m determined to get this law passed.”
She added: “The least we can do is offer our protectors some protection.
“Not only that, but if this in some small way acts as a deterrent for people thinking of committing crimes or who live that sort of lifestyle to think ‘well actually if somebody is killed it will be a serious consequence not just a few years in prison’ and back to their normal life.”
The Attorney General’s Office (AGO) has been asked to review the killers’ sentences to consider if they were too lenient.
It may refer their cases to the Court of Appeal for judges to consider whether the sentences should be increased.