Ross Willox, 41, killed the 39 year-old youth worker at his home in Monkton, Ayrshire, on April 28 2019.
Emma was then reported missing by her parents Margaret and Ian two days later when she failed to turn up for work.
As her frantic family and friends began the hunt to find her, Willox did nothing to help in the search of his friend of 18 years.
He instead had earlier driven Emma’s body in the boot of a car before dumping the naked remains at the end of a remote track in Glentrool Forest, Dumfries and Galloway.
It was weeks after Willox was charged with the killing that Emma’s badly-decomposed corpse was uncovered.
Jurors convicted Willox of murder and attempting to defeat the ends of justice after a six week trial at the High Court in Glasgow.
Emma's emotional parents and sisters Miriam and Sarah were present to hear the verdict.
Lord Mulholland told Willox: "You know what the sentence for murder is - it will be life imprisonment.
"Be under no misapprehension, this was a foul crime on a young woman loved by her family.
"You would have visited upon them a lifetime of wondering if she was still alive had her body not been recovered as a result of the sterling work by the police and experts.
"It was in such a remote place and you had intended her body would never be recovered."
Willox showed no emotion as he lead handcuffed back to the cells. He will learn the minimum he will spend behind bars next month.
UK orders for Royal Navy ships support Scottish shipbuilding jobs while SNP may turn to Poland to build much-needed ferries – Murdo Fraser MSP
Emma had gone to Willox’s home in Fairfield Park, Monkton for drinks on the night of the killing.
The pair had known each other from when they worked together at Kilmarnock prison.
The trial heard claims married Willox had previously been intimate with Emma.
It is at the house prosecutors stated Emma was then murdered by means unknown.
Little is known as to what exactly happened there.
But, on April 30, her parents were visiting relatives in Brighton when her mum got a call from Emma’s employers at the Kibble Education Centre in Paisley that she had not turned up for work.
Margaret told jurors: "We were concerned because it was totally out of character. She was in touch every day. We knew something was wrong."
Police eventually forced their way into Emma's home in Kilmarnock that day finding only her beloved Westie dog Maverick unusually alone.
Ipswich murder: Three people, including Scottish man, jailed for murder of vulnerable 22-year-old Joe Pooley who was thrown into River Gripping
A huge nationwide appeal was launched to try and find her.
Her younger sister Miriam was asked during the trial by prosecutor Paul Kearney if Willox helped in any of the searches.
She replied: "Never. I thought that was strange. Why would he not be trying to find her?"
On May 6 2019, detectives announced they had fears Emma had come to harm.
Four days later, Willox appeared in court charged with her murder - even though, at that time, no body had been found.
He appeared in the dock despite the "extreme lengths" he had gone to in a bid to cover up the crime.
But, Mr Kearney told jurors "good police work" uncovered "a trail of evidence" pointing to his guilt.
This included Willox's Mercedes SUV being spotted on CCTV the day after the killing heading towards the area where Emma's body was eventually discovered.
His DNA was also discovered on a lever in Emma's BMW 1 series - described by a friend as appearing "abandoned" at her home.
It was odd as she was said to have been very particular about parking the motor right outside her flat.
It is thought Willox left it there after driving it from his home.
Police also discovered Willox had bought four bottles of bleach and rubber gloves at a local bargain store after the killing.
A Jaguar car driven by Willox was also examined by a police dog trained in the scent of dead bodies, which gave a "positive indication" at the boot area.
WIllox had also made searches of a friend's iPad including for "can police track your car' and for "blood".
Jurors were played Willox's police interview after he was held.
He denied Emma had been "lying dead" in his home.
He insisted the pair had been at his house before going to Emma's where she wanted to "continue partying".
After he then returned to Monkton, Willox said he only knew there was concern about Emma when her sister Sarah phoned him.
The callous killer admitted he did not take part in any search for Emma.
Detective Inspector Stephen Tennant put to him: "Your friend went missing, you have known her for 18 years, see her regularly.
"When she goes missing, you do not get involved to help find her?"
Willox: "I was not informed that there was a search."
Police called in the help of Professor Lorna Dawson CBE during Operation Solzen and the search of the 700sq/m Galloway Forest area, where Emma's body was suspected to be.
Soil expert Prof Dawson was asked to examine a number of items including Timberland boots worn by Willox.
Prof Dawson made her findings on June 11 - just 24 hours later Emma's naked remains were found hidden in Glentrool Forest.
There was a 92 % soil match from the boots compared to the earth which covered Emma's body.
But, he told police any other sighting of him in the area would have been to walk his dogs.
Mobile phone analysis also put him in and around the location.
Jurors were told Emma's body was so badly decomposed, a pathologist could not state what caused her death although she had an apparent injury on her neck.
Willox’s QC Donald Findlay had claimed during the trial Willox had no case to answer, but this was thrown out by Lord Mulholland.
Sentencing was adjourned for reports.