An experienced boxer who beat his mother so badly while in a drug-induced psychosis that paramedics could not tell if she was male or female has been jailed for more than seven years for her manslaughter.

Finn Henry, 21, thought his mother Suzanne Henry, 54, was a “demon or a devil” when he attacked her on May 1 last year inside their family home in Madeley, Staffordshire, punching her in the head and face and strangling her while she sat on the sofa.

Mrs Henry, who had previously begged her son to stop using drugs, was filming his bizarre behaviour at the time of the brutal attack, which happened during a six-minute period.

Northampton Crown Court heard on Monday that Henry had been addicted to ketamine, having first taken the drug when he was 16, and would regularly take other illegal substances including cocaine and cannabis despite pleas from his family and friends to stop.

He was jailed for seven years and four months by Judge Rupert Mayo, who said Mrs Henry would have “suffered greatly” during the sustained attack, which led to her death in hospital two days later due to a traumatic brain injury.

Prosecutor Maria Karaiskos KC told the court that at around 3pm on May 1, an ambulance had been called by Henry’s girlfriend after she had met him at Morrisons and seen him “going in and out of consciousness and falling to the ground hitting his head”.

Henry told paramedics he had taken ketamine and that he had not been taking his prescribed medication for anxiety and depression and was worried his mother would “go f****** mad” if she knew what had happened.

Paramedics wanted to take Henry to hospital but he refused and he later went for a drive with friends, with one noticing him “talking to himself, screaming and making weird noises, completely out of it”, the court heard.

At around 7.30pm, Henry told all of his friends to get out of his car and was acting strangely, referring to the “apocalypse” and that he “needed to disappear for a bit as he was fully dancing with the devil and did not want to do something he would regret”, Ms Karaiskos said.

He told his friends he would go home and get some sleep but a video taken by Mrs Henry before she was killed, likely to show him how he was behaving the next day, showed her son in a “loud and excitable state” before throwing two punches at the camera.

Ms Karaiskos said: “The mobile phone of the defendant’s mother stopped recording when it fell down.

“Six minutes later, the defendant picked the phone up. The phone at that stage captured his face. He was covered in blood.”

The court was told a neighbour heard shouting and banging and saw Henry topless outside on the driveway after the attack looking “confused” before running away and attempting to get into various properties before he returned to the scene.

The emergency services were called and paramedics initially could not tell if Mrs Henry was male or female due to the amount of swelling and blood on her face.

When police arrived, Henry was naked and arrested and was deemed not medically fit for interview until the following day.

He was initially charged with murder but pleaded guilty to manslaughter at Stafford Crown Court in November, which was accepted by the prosecution.

In mitigation, Ahmed Hossain KC told Northampton Crown Court on Monday that Henry “lives with the horror of what he did every day and will continue to live with that for the rest of his life”.

He said: “He comes from a good, decent, caring, loving, supportive family. His mother was described as someone he loved and his number one.

“He loved her more than words can describe. The tragedy of this case is at the highest level.

“He said he had no intention of ever using substances again and when released he wants to help others avoid any position like this and highlight the risks of drug misuse.”

Sentencing him to seven years and four months behind bars, with an extended sentence period of four years, Judge Mayo praised Henry, who showed no emotion in the dock, and his family for dealing with the court proceedings with “dignity and honesty”.

He said: “Suzanne Henry started your life and brought you up in a way that was firm and fair.

“Your sister and your father have put forward very moving tributes to her today and what makes this so sad and tragic is that I suspect you agree with every word they said. But you took her life.

“It was a life that was beyond value and no sentence I pass today can bring her back. You simply cannot value a life as special as hers.

“I sentence you on the basis that you were unlikely to have been able to form an intent to kill because of the adverse effects of the drugs you had taken, but that does not excuse what you did.

“You were an experienced boxer and it was a lengthy assault in which she would have suffered greatly.

“You have expressed genuine remorse and take full responsibility and you have taken steps to address your addiction to ketamine.”