PROOF – that is the key thing that is missing in unsolved murder investigations.

Evidence is what provides that proof, however, and when evidence missing, it makes it almost impossible for a team of detectives and investigators to get to put together a picture of a victim’s final moments.

Usually, there is someone out there who knows the key detail or details which could lead to the case being solved – part of the problem is that, more often than not, that person is the murderer themselves.

We look at another three cases of unsolved murders in north Essex, all of which present complex challenges to the authorities.

Sandra Grant

Last month marked 20 years since Sandra Grant was last seen by her family.

Ms Grant was a 48-year-old divorced mother of four who lived in Wellesley Road, Clacton, and was known to have visited a soup kitchen in the town.

She is then believed to have gone for a drink at a nearby flat with another man, but after leaving some time later, she was not seen again.

A few days later, she was due to meet one of her daughters, but never showed up.

There is still a case reference number, 03-001671, which people can quote if they have any information about Ms Grant, for the file is by no means closed.

In a statement released in 2013, Essex Police investigating officer Det Con Sue Jenkins said the force has “never stopped looking at this case”.

Brentwood Live: Missing - it is now 20 years since Sandra Grant was seenMissing - it is now 20 years since Sandra Grant was seen (Image: Essex Police)

She said: “Sandra’s children have been living a painful life during this past decade.

“They don’t know what happened to their mother nor why anyone hasn’t come forward with information which answers this key question.

“We have continued to work through the material which has come into the incident room from the public, but at this time there is obviously a key piece of information which is missing and is why we are making another appeal for people living the community to come forward.

“Someone working and residing in the seaside resort knows what happened to Sandra and we, and Sandra’s children, need them to contact us.”

Paul Duckenfield

Aged 41, Paul Duckenfield was last seen in Stansted Airport in September 2008.

A father of two, Mr Duckenfield was well known in the gym scene in West Midlands, Derbyshire and Nottinghamshire areas, and also ran a company called International Debt and Security Consultants in Derby.

He was also a suspected drug supplier, and officers believe the motive for his murder is linked to the distribution of steroids.

On the day he was last seen, he landed at Stansted Airport and was picked up by a business partner he had known for several years.

He had planned to return home to his family on September 19 or 20 by flying from East Midlands Airport to Faro, but never made the flight.

Since then, nobody has seen Mr Duckenfield of heard from him.

He had regularly visited  gyms and leisure facilities when he was in the Great Saling and Braintree areas, and police believe Essex is where Mr Duckenfield was murdered, on or around September 16.

Brentwood Live: Link - investigators believe Mr Duckenfield's death is linked to the distribution of steroidsLink - investigators believe Mr Duckenfield's death is linked to the distribution of steroids (Image: Essex Police)

Speaking on the ten-year anniversary of his disappearance, senior investigating officer, Det Con Martin Pasmore, of the Kent and Essex Serious Crime Directorate, issued a fresh appeal.

In 2018, he said: “Ten years on and life has become no easier for Paul’s wife, children, parents or wider family. They still want answers as to what happened to their loved one.

“Over the last decade loyalties will have changed and people may now feel able to come forward.

“If you know something about Paul’s disappearance or death but haven’t spoken to us, now is the time to take that step.

"His family don’t want to spend another ten years wondering.”

“We do believe there is every possibility that the answer to Paul’s death lies within the criminal fraternity and is linked to his apparent steroid dealing.”

Edward McMartin

After reporting someone had forced entry into his flat in November 2017, Edward McMartin was taken ill, and since then there have been question marks surrounding his death.

Aged 55, Mr McMartin died at a police station.

What happened in the hour leading up to Mr McMartin’s death involved an argument with a man called Anthony Lines.

The two lived next to each other in a manor house converted into flats in Courtauld Road, Braintree.

Lines, 35, kicked Mr McMartin’s door off the hinges and allegedly threatened him in the early hours of the morning.

Mr McMartin then fled and flagged down police officers.

Less than an hour later, he was dead.

Brentwood Live: Dispute - Mr McMartin was involved in a dispute with his neighbour, Anthony Lines, shortly before his deathDispute - Mr McMartin was involved in a dispute with his neighbour, Anthony Lines, shortly before his death (Image: Essex Police)

Lines later appeared in court and admitted using violence to secure entry to the property and criminal damage, but denied having a weapon or any intent to harm the victim.

A post-mortem examination proved inconclusive.

Speaking at the time, his family said: “We as a family are heartbroken at the unexpected death of Eddie, our gentle giant whose smile could light up a room.

"He was a much loved son, brother, brother-in-law, uncle, cousin and friend who will be sadly missed.

“We would like to thank the police in attendance, paramedics, investigation team and the family liaison officers for the care and attention shown towards Eddie and the family.

“We ask that we are given privacy to come to terms with this tragic news.”