Henry Long, one of the killers of Pc Andrew Harper, is applying for permission to appeal against his 16-year prison sentence.
The 19-year-old was acquitted of murder but admitted manslaughter after Pc Harper, a Thames Valley Police traffic officer, was caught in a crane strap attached to the back of a car driven by Long.
A judiciary spokesman confirmed Long’s appeal, which comes days after his co-accused, Jessie Cole and Albert Bowers, both 18, lodged applications seeking permission to challenge their convictions and their 13-year prison sentences.
The prison sentences given to all three have already been referred to the Court of Appeal by the Attorney General for judges to decide whether they were too lenient.
Pc Harper’s widow is campaigning for Harper’s Law, which would mean those who kill emergency workers are jailed for life.
Lissie Harper and her 28-year-old husband had been married for just four weeks when he and a Thames Valley Police colleague responded to a late-night burglary in Sulhamstead, Berkshire, in August last year.
More than 500,000 people have now signed an online petition supporting her campaign and she is due to meet Home Secretary Priti Patel next month for talks.