A woman who burned her ex-boyfriend so badly he was driven to euthanasia has been jailed for life in what police say is the first life sentence for an acid attack in the United Kingdom.

Berlinah Wallace, 49, was last week found guilty by a jury of throwing a corrosive substance with intent, but not guilty of murder.

Her three-week trial in the Bristol Crown Court heard Wallace laughed as she threw 98 per cent proof sulphuric acid over Mark van Dongen while he was asleep.

"If I can't have you, no-one else can," Wallace said during the attack.

Mr van Dongen, 29, was left paralysed from the neck down and suffered extensive burns, including the loss of sight in one eye and partial blindness in the other.

He also had to have part of his left leg amputated after developing an infection.

Mr van Dongen spent 11 months in intensive care, four of them in a coma, before being discharged from hospital into residential care home.

The Bristol court heard he took his own life in January last year by voluntary euthanasia in Belgium, where the courts had recognised his "unbearable physical and psychological suffering".

In sentencing Wallace to life in prison, Justice Nicola Davies said Wallace did nothing to help Mr van Dongen as he ran away screaming in pain.

"Your intention was to burn, disfigure and disable Mark van Dongen so that he would not be attractive to any other woman," Justice Davies said.

"It was an act of pure evil."

Mark van Dongen took his own life by voluntary euthanasia 15 months after the acid attack. ( Supplied: Avon and Somerset Constabulary )

Ex-girlfriend researched acid attacks online

The court heard Wallace researched sulphuric acid and the damage it could cause before the premediated attack, with a total 82 entries found on her computer.

One of the entries was a 2015 article reporting a trial in which a man was alleged to have forced or tricked his girlfriend to drink a glass of acid.

Throughout her trial, Wallace claimed Mr van Dongen poured the acid into the glass on her bedside table intending for her to drink it.

Justice Davies rejected that account, stating Wallace had sought to destroy the name and character of Mr van Dongen, who had been her "supportive partner" for five years.

A bodymap depicts the acid burns suffered by Mark van Dongen. ( Supplied: Avon and Somerset Constabulary )

The court heard Mr van Dongen had previously confided in friends about the abuse he endured from Wallace and that he told his father he was scared of her.

In the weeks leading up to the incident, Wallace made repeated phone calls to Mr van Dongen and his new girlfriend.

On the night of September 22, 2015, Mr van Dongen went to the flat he had shared with Wallace because he was concerned she would harm herself.

Just before 3:00am the next morning, while he slept in nothing but his boxer shorts, Wallace threw the acid on Mr van Dongen.

He ran screaming from the flat to a neighbour's property while Wallace sat on the sofa and called a friend, the court heard.

Wallace claimed the acid was purchased earlier in the month to clean her drains, but Justice Davies rejected that "lie".

"It was not a random purchase," Justice Davies said.

"You removed the label from the bottle containing the colourless fluid which stated that the acid causes severe burns and eye damage.

"You did so to prevent detection of the acid in your home. You chose your moment for the attack."

A similar bottle of the acid used by Wallace, which was thrown from this cup. ( Supplied: Avon and Somerset Constabulary )

The acid burned through 25 per cent of Mr van Dongen's body.

Burns surgery consultant Jonathan Pleat gave evidence that there had been no equivalent patient with similar extensive injuries following a chemical attack.

Another treating clinician said Mr van Dongen's physical appearance would never be restored to anything which could be described as normal, that he had been permanently and irrevocably drastically disfigured.

Justice Davies said despite reports Wallace had a difficult childhood, nothing could excuse her actions.

"Life imprisonment is the only sentence which reflects not only the nature of your offending, but the continuing risk which you pose," she said.

Wallace will have to serve at least 12 years behind bars before she can be considered for parole.

'Only losers in this case'

The acid burnt the white bed sheets black. ( Supplied: Avon and Somerset Constabulary )

Mr van Dongen's father, Kess van Dongen, described in a victim impact statement the pain his son suffered after the attack.

"The fact that Mark, a 29-year-old man and recent graduate, decided to commit euthanasia, says something about the condition he was in and the amount of pain that he had been suffering," he said.

"He said: 'Dad, I am tired of fighting. I have suffered so much pain, I cannot take any more, please let me go'."

Kess van Dongen later said he was "very disappointed" about the outcome of Wallace's case.

"The court process has been a difficult and emotional experience," he said.

"There are only losers in this case. I hope that Mark can now rest in peace."

Senior Investigating Officer Detective Inspector Paul Catton said the investigation had been one of the most harrowing in all his years as a detective.

"Mark van Dongen suffered the most inconceivable pain imaginable following what was a cowardly attack borne out of jealousy," Detective Inspector Catton said.

"While the jury has concluded Wallace's actions did not amount to murder, we felt it was the right thing to do to ask them to consider the charge based on the evidence.

"In my view, it takes an unbelievably callous person to show absolutely no empathy or remorse for the level of suffering she caused."

Detective Inspector Catton said he believed Wallace was the first person to receive a life sentence for an acid attack.