Mark Martin was born on October 18, 1979, in Ilkeston, Derbyshire, England. He was the only child in his family. From a young age, Martin faced difficulties in school. He had a noticeable birthmark under his left eye, which made him a target for bullying. This treatment affected him deeply and contributed to his struggles as he grew up.

Martin's early life was marked by family challenges. His father was imprisoned during his childhood. It is said that his father shared a prison with the infamous Kray Twins, who were known criminals in the UK. By the age of 16, Martin had begun engaging in petty crime.

In his early 20s, Martin got married. However, this relationship was troubled. In 2002, he violently attacked his wife, which led to their separation in 2004. After this, he found himself homeless. He lived on the streets of Nottingham and often slept rough.

While living on the streets, Martin became part of a group of homeless individuals. Along with two associates, John Ashley and Dean Carr, he gained a reputation in the homeless community. They were feared by others and often stole from fellow rough sleepers. Martin was known by the nickname "Reds," while Ashley was called "Cockney John." He was seen as the leader of this group, described as a violent and aggressive person with a short temper.

On the night of January 24, 2005, Mark Martin was in a derelict flat in Nottingham with two men, John Ashley and Dean Carr, and a homeless woman named Ellen Frith. During that night, Frith started to eat an apple. Martin then attacked her, grabbing her by the throat and strangling her. After killing her, he used a syringe on her leg and set the flat on fire as he and his associates fled the scene. Firefighters discovered Frith's body when they extinguished the fire.

A man who had been in the flat the previous night reported to the police that Martin, Ashley, and Carr were present with Frith. Police quickly located Ashley, who claimed to have seen Martin strangle Frith. Martin later called the police and hinted at his involvement in the murder by saying, "I think you want me for murder." Afterward, Carr was arrested and also informed the police that Martin and Ashley were responsible for Frith’s death.

When Martin was questioned by police, he answered all questions with "no comment." He and Ashley were charged with Frith's murder. In the following days, Martin hinted in interviews that he had committed other murders. Investigators looked into two other homeless women, Katie Baxter and Zoe Pennick, who had gone missing. Martin had reportedly boasted about his involvement in their deaths. Baxter had been missing since December 2004, and Pennick was last seen on December 31, 2004.

Police investigation revealed that Martin had lured Baxter to his tent with the promise of cigarettes before strangling her. In February 2005, police excavated the area near Martin’s tent and found the bodies of both Pennick and Baxter. Forensic evidence indicated that they had died between December 30, 2004, and January 6, 2005.

Martin and Ashley were eventually charged with the murders of both Pennick and Baxter. Charges against Ashley for Frith's murder were dropped. Carr was later charged with Frith's murder but not with the other killings. In January 2006, the three men were tried at Nottingham Crown Court. Several witnesses from the homeless community testified about the men’s confessions. Despite pleading not guilty, all three were convicted.

Carr received a life sentence with a minimum of 14 years. Ashley was sentenced to at least 25 years. Martin, being the main perpetrator, was convicted of all three murders and was given a life sentence with a whole-life tariff, indicating he would likely never be released from prison. Martin was later referred to by the media as the "Sneinton Strangler."