Police were led to Jill Meagher’s killer, Adrian Bayley, by tracing her mobile phone signal and then his.

When Melbourne woman Jill Meagher vanished after a night out in September 2012, it was her mobile phone signal that led detectives to her rapist and killer.

More than two years later, when NSW school cleaner Vincent Stanford raped and murdered bride-to-be Stephanie Scott, it was his phone’s location that enabled police to find the young teacher’s body.

Late last year, the mobile phone signal of missing Melbourne woman Karen Ristevski gave detectives a major breakthrough.

Her disappearance in June initially baffled police.

Karen Ristevski’s body was found by a bushwalker this week, wedged between two logs. Picture: Nicole GarmstonSource:News Corp Australia

But late last year, it was revealed pings from phones belonging to both her and her husband Borce placed them both on the Calder Freeway, near Gisborne, the day she went missing.

A search area was centred near where her mobile was last located.

Two months on, a bushwalker discovered her decomposed body wedged between two logs in the Macedon Regional Park, about 25km from the search area.

Charges are yet to be laid over Ms Ristevski’s death.

While killers dumping bodies in remote bush locations is nothing new, placing them at crime scenes has never been easier, thanks to the ubiquitous 21st century mobile phone.

Unfortunately for detectives, however, the technology can only be used as an aid in investigations.

Private investigator Scott Ross told the Diligentia Group said while mobile phone pings have helped solve crimes, it can’t be taken as hard evidence, like DNA.

Unbeknown to many, however, is that even if a phone is turned off, it runs a hidden operating system that is always turned on.

The system constantly sends pings to phone towers and is always searching for the closest or strongest signal.

Even when your phone is off, it sends pings towers in range. Picture: Chris McCormackSource:News Corp Australia

The towers keep a log of those pings.

The constant stream of pings between multiple towers allow investigators to triangulate a phone’s location based on the strength at each tower.

A phone’s location can be more accurately pinpointed when there are more phone towers, so in cities people can be tracked constantly.

According to The New Yorker, there are some things your mobile phone can’t tell police and the pings don’t always point to a person’s guilt.

Karen Ristevski's mobile phone pings.Source:Supplied

A woman named Lisa Marie Roberts, from Portland in the US, served almost 10 years in prison for a crime she didn’t commit.

She was convicted on mobile phone pings that placed her at the crime scene.

Roberts was found guilty of strangling her girlfriend Jerri Lee Williams, who had a history of drug use and prostitution, in 2002.

During the investigation police found Roberts made a call that bounced off a mobile tower less than five kilometres from where Williams’ body was found.

The chief executive of Cherry Biometrics, a company of mobile tower and mobile phone tracking experts, told The New Yorker towers were not always completely reliable.

Michael Cherry said the assumption was when you made a phone call, your phone bounced off the closest tower and from that alone, police could identify your exact location.

He said that’s not how it works.

But for a number of high profile cases in recent years, mobile phone towers have provided homicide investigators with the crucial breakthrough.

ADRIAN BAYLEY

HAD the killer of Melbourne woman Jill Meagher not carried her phone with him when he dumped her body beside a remote country road in 2012, she may still be in her shallow, lonely grave.

In a case that rocked Australia, Bayley accosted Ms Meagher in Brunswick as she walked the short distance to her home from a nearby bar, in the early hours of September 22.

After raping and murdering her in a laneway, he returned to his home for his car, which he then used to transport her body.

Adrian Bayley initially denied involvement in Jill Meagher’s death.Source:Supplied

The movement of Jill Meagher’s mobile phone led police to her killer.Source:Supplied

Ms Meagher’s mobile phone signal revealed she had remained in the Brunswick area until 4.24am, when it began to move.

Pinging on mobile phone towers revealed it moved north along the CityLink toll road in the vicinity of Moreland Road at 4.40am and then continued north along the Calder Freeway to Sunbury.

CityLink records led police to Bayley — and his mobile phone records — obtained by detectives, revealed its movements that morning were identical to those of Ms Meagher’s phone.

Bayley was arrested and, during questioning, broke down and confessed when presented with Ms Meagher’s broken Vodafone SIM card, which his partner had found in the bottom of her washing machine.

He led police to her body and was later sentenced to life in jail.

The lonely bush grave, where Bayley buried Jill Meagher after raping and killing her.Source:News Limited

VINCENT STANFORD

The rapist and murderer of schoolteacher Stephanie Scott had confessed to his crimes five days after she went missing but the exact location of her charred body remained a mystery.

The much-loved 26-year-old was days away from being married when she was raped and murdered by Leeton High School cleaner Vincent Stanford on Easter Sunday, 2015.

The 25-year-old cleaner then used the bride-to-be’s car to drive her naked body to Cocoparra National Park, about 70km northeast of Leeton, where he set it alight.

Vincent Stanford’s mobile phone location enabled police to find Stephanie Scott’s body.Source:Supplied

The much-loved teacher was murdered days before her wedding.Source:Supplied

Stanford confessed to the crime after his alibi that he was shopping at a local grocery store at the time of Ms Scott’s murder came unstuck, when a simple police check found the store did not open on Easter Sunday.

But it was not he who led police to her charred remains but his mobile phone signal.

Officers said a triangulation of phone towers in the area helped them narrow the search area, which enabled them to find her body, dumped just five metres from a remote dirt road in dense bushland.

Stanford pleaded guilty to murder and was sentenced to life in jail.

He told police he killed Ms Scott because, “He wanted to kill”.

DANIEL HOLDOM

It’s not just the advent of smartphones with their GPS location services that have aided police in murder investigations.

Back in 2008, Daniel James Holdom allegedly killed 20-year-old Karlie Pearce-Stevenson in the Belanglo State Forest on either December 14 or 15.

Five days later, he allegedly murdered her two-year-old daughter, Khandalyce Pearce and dumped her body in a suitcase beside a South Australian highway.

Karlie’s skeletal remains were not found until 2010, while the discovery of the toddler’s body was not made until 2015.

Daniel Holdom is awaiting trial for the double murder.Source:Supplied

Karlie Pearce-Stevenson was just 20 when she died.Source:Supplied

The two bodies, dumped 1000km apart, were not initially thought to be connected, however a tip-off to Crime Stoppers led to DNA testing that confirmed they were mother and daughter and investigators were, most likely, hunting a double murderer.

Holdom was charged with Karlie’s murder in 2015, after police traced a phone that allegedly belonged to the 41-year-old through pings off mobile phone towers in the Belanglo State Forest.

The pings allegedly put the phone near the location where Karlie’s remains were found, at about the time of her death.

He was later also charged with Khandalyce’s murder.

Holdom is yet to stand trial.

The bodies of Khandalyce Pearce and her mother, Karlie Jade Pearce-Stevenson, were dumped 100km apart.Source:Supplied

TODD KOHLHEPP

In the case of US woman Kala Brown, police were able to use pings from mobile phone towers to rescue her before she became a victim of alleged serial killer Todd Kohlhepp last year.

Police discovered the 30-year-old, allegedly chained up like a dog inside a shipping container on Kohlhepp’s 95-acre property in South Carolina, two months after she and her boyfriend, Charlie Carver vanished.

Alleged serial killer Todd Kohlhepp.Source:AP

Kohlhepp, a registered sex offender, allegedly shot Mr Carver dead in front of Ms Brown.

The bodies of another couple in their 20s, Meagan and Johnny Coxie, were also found on his property.

Police were able to find the terrified Ms Brown by tracing the last pings her phone transmitted before her phone battery died.

Pings were sent between multiple towers, which allowed investigators to triangulate the phone’s location based on the strength of the signal received by each tower.

When they obtained a warrant to search Kohlhepp’s property, officers heard frantic banging from inside a metal shipping container where they found Ms Brown, alive, but allegedly “chained like a dog” by the neck and ankle.

Police found Kala Brown chained up inside a shipping container.Source:Supplied

Kohlhepp was later charged with a total of seven murders.

Kohlhepp is yet to go to trial.

The shipping container in which Ms Brown was allegedly held captive for two months is seized by police as evidence.Source:AP