It just didn’t make sense – she was full of life and independent and she adored her three kids. But in August last year 30-year-old Kellie Sutton was found hanged in her home, leaving her loved ones devastated and baffled. There had to be more to it, her family said. As far as they knew she hadn’t suffered from depression and she’d never willingly have left her children without a mother. The authorities ordered an investigation into the young woman’s death – and the outcome is something that’s changed the course of UK legal history.The probe found that Kellie, who’s from Welwyn Garden City in Hertfordshire, north of London, had been driven to suicide, and in a recent landmark ruling her boyfriend was sentenced to four years and three months behind bars. “You beat her and ground her down and broke her spirit,” Judge Philip Grey told Steven Gane (31) in his no-holdsbarred judgment. Gane was found guilty of coercive control – also known as gaslighting – which was criminalised in the UK in 2015. This was the first time a conviction had been handed down after the death of a victim, and British police welcomed the sentence as a milestone for the new legislation. The term gaslighting comes from the 1944 Oscar-winning thriller Gaslight starring Ingrid Bergman, in which a killer tries to slowly manipulate his wife into thinking she’s going crazy. The couple have gaslights in their home and when the husband switches the attic lights on, the lights in the rest of the house become dimmer. But when the woman asks her husband what’s going on he tells her she’s imagining things. Gaslighting is a tactic used to gain power and control and is a common technique employed by abusers, dictators, narcissists and cult leaders. Kellie’s devastated mom, Pamela Taylor, said what Gane, a former soldier, did to her beautiful daughter has left her heartbroken. “He made her feel worthless and unloved. Nothing could be further from the truth. Long after he’s out of prison we shall still grieve her loss.”It was Gane who discovered Kellie hanging from a rope around her neck. She was unconscious but never came to, and life support was switched off three days later. Just five months earlier Kellie had been positive and vivacious – then she met Gane in a pub near her home. Not long afterwards she’d transformed into a quiet, anxious person. Her friend Alexia Spathas (30) says she knew straightaway there was something off about Kellie’s new boyfriend. “She was a single mom with three kids [aged between four and 14] and he must have sensed she was vulnerable,” Alexia says. Within weeks Gane had moved in and started doing things around the house and buying things “to make her feel like she relied on him”, Alexia adds. “I told her to stay away from him because he seemed controlling.” Pamela was just happy her daughter had “someone in her life” – but in court she discovered just how badly her daughter had been abused. “Having to listen to what she went through was harrowing. He’s pure evil. “We were close but Kellie never told me anything was wrong. I know why – she didn’t want to upset me. And when ever I was with them he was fine. To me they were like a normal couple.” But behind closed doors Gane subjected Kellie to what the judge described as “domineering and grossly humiliating behaviour”. He was physically violent, pinning her to the floor and throttling her because she’d gone out without telling him.Other forms of abuse were more subtle.He kept her bank card, and searched her bedroom to see if men had been there. He called her a slut and accused her of cheating on him, even sniffing her underwear to see if she’d been unfaithful. Disturbing messages Kellie sent to Gane were read out during the two-week trial, painting a picture of a toxic relationship. “I’m fed up of this s**t prisoner life,” she wrote in one. “All you’re going to do is moan and beat me all afternoon,” another read.Things escalated when Kellie had been due to visit her middle child, who lives with her paternal grandparents in Bournemouth in the south of England. She and Gane fought before she left and Kellie ended up in hospital with a 3cm gash in her head. “She told us they were play-fighting and she banged her head,” Pamela recalls. “Now I wonder if it was to stop her going away.”This isn’t the only gaslighting case to have made headlines in the UK recently. Natalie Lewis-Hoyle (28), the daughter of British MP Miriam Lewis, was found hanged in her home in Heybridge, Essex, in December. Miriam says Natalie was driven to take her own life because she was in psychological torment”from her two-and-a-half-year toxic relationship with her boyfriend, and it affected the whole family.Miriam has now launched a website to raise awareness about gaslighting. “Natalie was a really feisty character and you wouldn’t think it would get to her,” she says. “But quite often the people who are controlled in relationships are in fact intelligent women because they overthink and try to rationalise it. They don’t realise what’s happening.” Unlike in Kellie’s case, an inquest found no third party had been involved. “I accept the outcome,” Miriam says. “But this isn’t something I’m going to be able to put out of my head. She was a tiny person – a teeny, tiny person. She was a pocket rocket, just a whole bundle of energy.” Now she’s gone, Miriam says. And she’s determined to stop it from happening to other people. More about gaslightingIt’s an attempt to manipulate someone’s reality, says Professor Gérard Labuschagne, former head of the SAPS investigative psychology unit. “A classic technique is to move things around or let strange things happen to make a person believe they’re unstable or mentally disturbed.” He says most often gaslighting is done with a goal in mind, such as to get control of children or finances. It’s a “sophisticated form of emotional abuse where victims end up questioning their instincts and feelings”. It can take months or even years before the victim realises what’s going on. Your self-image suffers and your emotional capabilities are restricted, says Dr Elmari Mulder Craig, a Pretoria sexologist and relationship therapist. “You start to believe everything is your fault, and if you only did this or that differently the relationship could improve.” If you’re a victim of gaslighting, seek professional help as the situation is unlikely to get better by itself, she advises. Also confide in a close friend or family member who can help you make sense of your reality – what’s acceptable behaviour and what isn’t.Warning signs: Questioning yourself all the time and worrying you’re being oversensitive. Feeling overwhelmed and as if you’re losing your mind. Constantly apologising to your friends and family for your partner’s behaviour. Withholding information from your family so you don’t have to explain things. Lying to yourself about what’s going on. S Battling to make even simple decisions. Feelings of hopelessness.