A number of strong leads are being followed up by police investigating the murder of teenage model Sally Anne Bowman after a BBC Crimewatch appeal.
More than 100 calls from members of the public were received and half named possible suspects, police said.
Det Ch Insp Stuart Cundy said there was a "strong chance" an attack on a woman in 2000 could be linked to the 18-year-old's murder on 25 September.
Miss Bowman was stabbed outside her home in South Croydon, south London.
Her body was found in the early hours of Sunday. She had also been sexually assaulted.
Det Ch Insp Cundy said police were now following up on 50 different names of possible suspects provided by Crimewatch viewers.
"It's going to take a long time to work through this," he said.
Police have released CCTV footage showing Miss Bowman, 18, with friends in Lloyds Bar, Croydon, hours before her death.
The suspect is white, in his 20s or 30s, with short brown hair
The CCTV footage followed Miss Bowman as she bought drinks at the bar, chatted with friends then left with her sister at 0100 BST before going to a friend's house.
At 0200 BST she is seen coming back into town in a taxi and about 20 minutes later her ex-boyfriend picks her up and drives her home to Blenheim Crescent, South Croydon.
Detectives believe there is a high chance the man had been lying in wait for her outside her home.
An e-fit of Miss Bowman's killer has been released and the Met Police and the Sun newspaper have offered a joint reward of £40,000 for information leading to a conviction.
It is thought the man lives or works locally and police said they may carry out DNA tests on men under 40.
DCI Cundy believes the man they are looking for is a serial sex attacker who may have committed about six other assaults.
Miss Bowman's murder has been forensically linked to a sex attack in nearby Purley in 2001.
It is thought the same man also attacked and robbed another woman just hours before killing the model.
DCI Cundy said the victim described her attacker as good looking.
"She thinks and I agree there is a very strong chance he has got a partner or girlfriend and I would appeal if you have a suspicion about someone you know, please contact us," he said.
The attacker is described as white, in his 20s or 30s, between 5ft 9in and 6ft and of medium build with short brown hair.
Sally Anne's family have been paying tribute to the teenager, saying she was "the most caring young lady you could ever wish to meet".
They described her as a lively, ambitious, and beautiful young woman who had been intent on achieving everything she set out to do in life.