Police have released an e-fit of a man seen near the scene of an attack being linked to the murder of Marsha McDonnell.
The witness came forward after seeing a Crimewatch reconstruction
Marsha, 19, a gap-year student, was killed near her home in Hampton, south west London in the early hours of 4 February after a night out with friends.
The e-fit has been drawn-up with the help of a witness who saw the man leaning over a 17-year-old girl who was left with head injuries after being attacked on 8 January.
The suspect then walked away from the girl in Walpole Gardens, Strawberry Hill, towards Spencer Road, at about 2100 GMT.
The girl woke up in hospital and it was initially assumed she had slipped on ice as she could not remember being attacked.
But her family reported the incident to police following the death of Marsha, who was hit over the head with a blunt instrument.
A few weeks after Marsha's death an 18-year-old boy was attacked by a hooded man who lunged at him also with a blunt instrument in nearby Hampton Hill. He escaped unhurt.
Marsha was attacked after a night out with friends
The three attacks took place within a mile of each other and police believe the same
man is responsible for them all.
The new witness came forward following a reconstruction on the BBC's Crimewatch.
The suspect is described as white, late 40's about 5ft 9ins, chunky build with dark collar length hair, bushy eyebrows and clean shaven.
He had a round prominent nose and was wearing a dark-coloured thigh length waxed jacket.
Police are appealing for anyone who recognises this man to come forward.