91�ȱ�

A hologram of a young sex worker haunts Amsterdam’s red light district.

Dressed in faded denim hotpants, a leopard-print bra, with a tattoo snaking up her stomach and across her chest, the 3D computer-generated image reaches out and appears to knock on the window to attract attention.

She leans forward, breathes on the glass and writes the word "help".

The hologram is designed to represent Bernadette "Betty" Szabo, a 19-year-old woman from Hungary who was murdered a few months after giving birth in 2009.

Her fatal stabbing has baffled police for 15 years. Dutch cold case detectives are using the innovative technology for the first time in an effort to solve the case.

The murdered teenager’s image is being projected from behind a window, alongside hundreds of young women who continue to make a living in this notoriously risky industry.

Investigators hope the lifelike hologram will help jog memories and draw attention to the unsolved murder.

Until now, Betty's killer has eluded justice and cold case detective Anne Dreijer-Heemskerk is determined to change that: “A young woman, only 19, taken from life in such a horrific way.”

Szabo had a tough life and her story was one of hardship and resilience, according to the detective.

She had moved to Amsterdam aged 18 and became pregnant soon afterwards. She carried on working throughout her pregnancy, returning to the job shortly after her son was born.

It was in the early hours of 19 February 2009, when two sex workers went to check on the teenage mother during a break between clients, because they realised her usual music was not playing.

When they entered her brothel, a small room with a plastic-covered bed, vanity table and sink, they discovered Betty Szabo's body.

She had been murdered three months after giving birth, the victim of a savage knife attack.

Her baby was placed in foster care and never got to know his mother - a fact that motivates detectives.

Although police immediately launched a murder investigation, her killer was never found. They combed through CCTV footage and questioned potential witnesses.

The majority of people eyeing the scantily dressed women behind the red neon windows are tourists. Police suspect the perpetrator came from abroad.

Now they are urging people who may have visited Amsterdam to think back, with a €30,000 reward to encourage witnesses to come forward.

As Amsterdam grapples with controversial plans to relocate its famous brothels to an out-of-town "erotic zone", Betty Szabo's hologram offers a poignant reminder of the vulnerability of sex workers in an area that, despite a range of security measures, remains perilous.

Sex workers have voiced concerns that removing the women who sell sex from public view could expose them to even greater danger.

The fact that such a violent crime could occur in one of the Netherlands' busiest nightspots without witnesses coming forward continues to confound investigators.

In the historic red-light district where she once lived and worked, the teenage sex worker’s digital presence reminds passers-by that her case is yet to be solved.