Five murder cases linked to cannabis use in just a single year
Mental health deterioration and psychotic episodes blamed on the increased potency of marijuana are factors in several court cases
CANNABIS-INDUCED psychosis featured in five murder cases before the courts last year amid warnings more young people are becoming addicted to the increasingly potent drug.
The revelation comes after Garda Commissioner Drew Harris recently warned that higherstrength cannabis is causing psychosis and long-term mental health issues.
Cannabis is Ireland’s most popular drug followed by cocaine, heroin and synthetic opioids.
The State’s health agency reiterated the Commissioner’s concerns this weekend. A spokesman for the Health Services Executive (HSE) said that the chemical component responsible for the psychoactive effects associated with the drug has become ‘much stronger’ in recent times.
The HSE also said cannabis dependency is now ‘more common’ than alcohol among young people in Ireland.
The spokesman further warned that evidence of research has found ‘people who use cannabis in their teens have an increased risk of developing a significant mental health problem such as psychosis or schizophrenia when compared with noncannabis users’.
Long-term cannabis use can also exacerbate any existing mental health problems, the HSE added.
The warnings over the increasing potency and dependency on cannabis come amid worrying signs that the drug has become a feature in a growing number of violent murders.
Last month a man who killed and decapitated his wife while suffering from a cannabis-induced psychotic episode was found not guilty by reason of insanity.
The court heard that Diego Costa Silva attacked Fabiola Camara De Campos Silva at their home in Finglas, Dublin, and then removed her head because he thought that she had been possessed by a serpent.
Dr Brenda Wright and Dr Mark Joynt both agreed Diego Costa Silva’s psychosis was not due to acute intoxication from cannabis, but a more persistent illness of cannabis-induced psychosis. They told the trial that cannabisinduced psychosis is a mental disorder under the Criminal Law (Insanity) Act 2006.
They agreed that, as a result of his disorder, Mr Costa Silva did not understand the nature and quality of his actions, nor was he able to realise that what he was doing was wrong.
In June 2023, a woman undergoing a psychotic episode when she stabbed a stranger to death was given an eight-year prison sentence by the judge presiding over the case at the Central Criminal Court.
Christina Anderson’s husband told her trial that they were smoking an average of €200 to €250 worth of cannabis per month in the lead-up to the killing.
During the trial, defence counsel Michael O’Higgins SC raised the issue of whether Ms Anderson’s actions when she stabbed Gareth Kelly to death outside her home were driven by mental illness or cannabis intoxication.
The State accepted Ms Anderson was undergoing a psychotic episode at the time of the killing and cannabis intoxication did ‘not feature’ in the case.
Last May a 32-year-old man was sentenced to 15 years in prison for the manslaughter of his on-and-off partner in Co. Donegal in 2019.
In that case, Richard Burke of Killygordon was found guilty of manslaughter by reason of diminished responsibility.
Jasmine McMonagle, 28, was strangled and beaten to death in her home in Co. Donegal in the early hours of January 4, 2019, while her two daughters were asleep upstairs.
The court was told that the Director of Public Prosecutions (DPP) sought assistance from an expert, with the jury hearing evidence from Dr Dervla Duffy, a consultant psychiatrist at the Central Mental Hospital.
Dr Duffy said that, in her expert opinion, Mr Burke did have a mental disorder – a cannabis-induced psychotic disorder – at the time of the killing.
Last April Stephen Silver, who shot Garda Colm Horkan dead with the garda’s own gun, was jailed for life for capital murder.
The court had heard about how Silver in the past had experienced psychotic symptoms that were on the ‘extreme end’ of his bipolar affective disorder.
Silver told the court that cannabis use impacted his mental health as it would bring on episodes.
He said he smoked his first joint when he was 17 or 18, but then took a break from using cannabis after he had been ‘smoking with a friend of mine and I ended up hitting him for no real reason.
‘I thought he was doing me bad. I stopped smoking it then.’
Another case that came before the courts last year heard how a man accused of murder had suffered a psychotic episode due to ‘the long-term effects of chronic cannabis exposure’.
Meanwhile, sources in the security industry said there have been an increasing number of arrests associated with cannabis under
‘The drug has recently become much stronger’
‘Cannabis-induced psychosis is a disorder’
‘Studies show it feeds anxiety and paranoia’
the Mental Health Act recently.
One source told the MoS: ‘We should be talking about this in light of calls to decriminalise [cannabis]. There have been a significant amount of people arrested around the country under the Mental Health Act recently.
‘In a large number of these cases substance abuse is central to it, both alcohol and drugs.
‘But certainly we have seen a significantly increased level of paranoia or suicidal tendencies because of drugs, primarily [due to] cannabis.
‘Lots of anxious students swear that cannabis calms them; however the medical studies show it actually feeds anxiety and depression and paranoia.’