Hertfordshire has seen many a gruesome and grizzly crime, but not all of them have been solved.

Here are five mysterious unsolved murders that shocked the county.

1. 'Baldock Woman'

By far the most mysterious case on our list, investigators are still trying to find who 'Baldock Woman' was and who killed her.

At 6.15am on February 18, 1975, the young woman was struck by one or more vehicles on the A1 near Baldock.

48 years on, she has not been identified, and her killer has not been brought to justice.

Investigators believe she was aged between 17 and 25, and witnesses who saw her just 45 minutes before she was killed believe she was French and heading for London.

Welwyn Hatfield Times: The murdered woman was wearing this Afghan coat at the time of her death.The murdered woman was wearing this Afghan coat at the time of her death. (Image: Locate International)

She was also wearing a distinctive Afghan coat.

Following a 2010 appeal, couple David and Barbara Liversedge came forward claiming the victim was a French student named Odile.

David met her in 1972 when she was hitchhiking on London’s North Circular during a thunderstorm, and she stayed with them in the early 1970s.

The young woman who stayed with the couple was between 23 and 25 years old and had said that she was from north of Paris or had lived in the northern part of Paris.

Last year, Locate International launched another appeal to find out more about 'Baldock Woman'.

2. Deep freeze murder

On December 30, 1957, Anne Noblett disappeared while travelling to her home in Marshalls Heath, Hertfordshire.

A month later, on January 31, 1958, her fully clothed body was found in Rose Grove Woods near Whitwell, Hitchin. The remains of the 17-year-old showed signs of refrigeration and the case was dubbed the "Deep Freeze Murder" by the press.

On the night of her disappearance, Anne had attended a dance at Lourdes Hall in Harpenden. After the dance she caught the 391 Green Line bus to return home to Marshalls Heath, where she lived with her parents and brothers.

Welwyn Hatfield Times: Anne's body was found in woods near Whitwell.Anne's body was found in woods near Whitwell. (Image: Archant)

The last sighting of Anne was by Shirley Edwards at around 6pm, when she alighted the bus at the Cherry Trees pub at the bottom of Marshalls Heath Lane.

A resident reported the rear lights of a car being visible further up the lane at the time of her disappearance.

Her body was found by two dog walkers, and police determined she was strangled and most likely sexually assaulted. Her body was also frozen solid, which investigators established was due to refrigeration.

Due to a lack of evidence, especially DNA, it is unlikely that Anne's killer will ever be found.

3. Colney Heath shooting

Late on the night of August 26, 1971, John Augustus Roden Orde, owner of Tyttenhanger Farm in Colney Heath, was shot dead.

He was doing his usual rounds when, on a track near Coursers Road, he came across a group of people trying to steal the rear number plate from his Ford Cortina.

He was shot by someone in the group, and a 32-year-old man was arrested two months after the murder, when police raided his home and found two revolvers and 365 rounds of ammunition hidden inside a barrel of grease.

The man's sister told investigators that he has confessed to the murder, and he was tried but found not guilty.

John's killer has never been identified.

4. Cuffley Station suicide pact

The death of Frederick Walter Read, an aircraftman and a corporal from Cuffley, is one straight out a murder mystery book.

Frederick was shot in the back during an alleged suicide pact with his girlfriend near Cuffley Station on May 30, 1939.

His body was found by the railway tracks, while his girlfriend was found staggering across the railway line with a wound to her stomach about 300 yards from Cuffley Station.

Welwyn Hatfield Times: Frederick's body was found near Cuffley Station in 1939.Frederick's body was found near Cuffley Station in 1939. (Image: Archant)

She was taken to Wellhouse Hospital, Barnet, but told doctors "I want to die, let me die", when they tried to treat her. She was given a blood transfusion and survived.

She claimed that Frederick shot himself in the back and that she then shot herself in her stomach before putting the pistol back in his hands.

A doctor determined that it was almost physically impossible for Frederick's wound to be self-inflicted, but there was a remote chance that he had held the pistol with his left hand and operated the trigger with his thumb.

His girlfriend told police they had both agreed to take their own lives, but she later denied saying this and was tried for his murder, but she was acquitted after no evidence was offered.

What happened that day in 1939 will likely forever remain a mystery.

5. Antique store murder

On November 9, 1998, Denise Motley was battered to death with a parking post on the stairs leading to the basement of the Hitchin antiques shop she owned with her husband.

Drug addicts were intially thought to be behind the murder, with the store located in an area where they frequently raided businesses.

But, after police probed the private life of her husband, Stuart Motley, and found he had been cheating on her, he was arrested and charged with her murder.

He was found not guilty after a seven-week trial, but was later jailed for 12 years in 2004 after Irish police seized €1.5 million worth of heroin from him.

At the time of Denise's murder, he told reporters: "Denise and I did everything together and she was my best friend.

"I feel lost without her and I do not know where I go from here. I have to keep going for the sake of my daughter."

Denise's killer has never been identified.