Three men jailed over a fatal stabbing in Greenford have been told their "severe" sentences are "necessary" to deter others after their appeals were rejected.
Miguel Leiba, 18, Ryan Beresford, 20, and Michael Mensah, 19, were convicted of the manslaughter of Dean Mayley, 24, who had the mental age of a nine-year-old, in October 2014.
Mensah, Beresford and Leiba were all found guilty of manslaughter and attempted robbery. Mensah was also convicted of a separate robbery.
Leiba, of Goldsmith Road, Acton, was jailed for 14 years while Beresford, of Winchester Street, Acton, received a 15-year term, and Mensah, of Brants Walk, Hanwell, got 17 years.
Jamal Jones, who did not challenge his sentence, was sentenced to 15 years for murder.
Only Mensah had previous convictions, which were for possession of a taser, a samurai sword and a combat knife.
On Wednesday (September 23) at the Criminal Appeal Court, lawyers for all three argued their sentences were too tough and should be reduced.
But Lord Justice Lloyd Jones said the judge who jailed the trio had taken "sufficient account" of their youth and "lack of maturity". He also had regard to the previous good character of Leiba and Beresford, the court was told.
Each of them had "assisted or encouraged a robbery, knowing Jamal Jones had a knife and each one realised he might stab Dean Mayley", the appeal judge added.
He said use of knives was "rightly" a cause of public concern and sentences must reflect the "need for deterrence".
"These were severe sentences and they will result in these young men spending many years in detention," the judge ruked. "However they were necessary if others are to be deterred from knife crime."
Lord Justice Lloyd Jones, who was sitting with Mr Justice Blake and Mr Justice Haddon-Cave, refused the appeals against sentence.
Leiba also failed in a challenge to his convictions.
The victim, from Northolt, was stabbed in the heart by Jones while walking alone in Ruislip Road, on February 7 last year.
At 5.15pm, he was approached by Jones, who had a knife, and was told to hand over his North Face jacket.
Because of his mental age, Mr Mayley would not have realised the risk in refusing to comply, said the judge.
Beresford and Leiba were standing nearby when Jones stabbed Mr Mayley.
All three ran off and left in a car driven by Mensah, Lord Justice Lloyd Jones told London’s Appeal Court.
The prosecution case was that the four were acting as a "team of knife-point robbers", driving around looking for victims.
