Petri Kurti was told hewould serve a minimum of 11 years and four months. Zoheb Majid, 20, was jailed for 10 years for robbery and manslaughter.
Schoolboy Kurti is one of the youngest convicted murderers in Britain.
Glynis Bensley, 47, was on her way from from a pub in Smethwick in September last year when she was attacked by the pair.
Kurti hit Glynis from behind and, as she fell to the ground, he was joined by Majid. The young boys then stamped on their victim’s face with such force, an imprint of his foot was left on her cheek.
After the attack, which lasted just 32 seconds, the pair robbed Glynis of all the belongings she had. A post mortem later showed Glynis died as a result of severe bleeding on her brain.
Following the case, police believe Glynis was a victim because she was in the wrong place at the wrong time, with Detective Chief Inspector Sam Ridding saying: “Ms Bensley was tragically in the wrong place at the wrong time and was randomly picked out by the pair believing that she was a man and that she was wearing a gold bracelet.”
After the verdict, Glynis’ sister Dawn spoke of the family’s pain at losing Glynis.
“We are a very close and supportive family and always look out for each other,” Dawn said. “To try and explain how Glynis’ murder has affected us is very hard to put into words.
“Glynis was my only sister and best friend. I would describe her as my right arm and I thought we would grow old together.”