Monaghan, 30, has today (Friday, December 17) been found guilty of all three murders following the conclusion of a 10-week trial at Preston Crown Court.
The Blackburn dad had denied murdering his two children, Ruby, aged 24 days, and Logan, aged 21 months, and his partner, Evie Adams, 23, six years later in 2019.
But the jury has found him guilty of murdering all three, as well as the attempted murder of a third child who cannot be identified.
The 30-year-old, described as a manipulative and controlling gambling addict, was accused of obstructing the airways of his helpless children in separate murders in January and August, 2013.
He was on police bail for the suspected murder of his children when he killed his new girlfriend with a deadly cocktail of prescription drugs in October 2019.
Monaghan killed because he could not face rejection by his partners, Preston Crown Court heard during his 10-week trial.
The defendant, who has been suffering a minor illness, was not in court as the guilty verdicts were delivered by the foreman of the jury following 26 hours of deliberation across six days.
Laura Gray, the mother of the children, could be heard weeping in the public gallery as the verdicts were given.
Monaghan was convicted of the three murders and two counts of attempted murder to a third child who cannot be identified for legal reasons.
The trial judge, Mr Justice Goose, ordered the defendant to be brought from prison to the court for sentencing at 3pm.
"Justice has been done," say CPS
Following Monaghan's conviction, Martin Hill, deputy head of the Crown Prosecution Service (CPS) North West’s Complex Case Unit, said: "Jordan Monaghan’s cruelty is beyond belief and the ruthlessness of these murders is harrowing.
"It is difficult to comprehend the depravity that went into planning and committing these murders.
"Three innocent people needlessly lost their lives due to Monaghan’s utter selfishness.
"Together, the CPS and Lancashire police were able to build a strong case against him by ensuring all possible medical explanations for the deaths of the children could be discounted.
"I cannot begin to imagine the pain and suffering that Monaghan’s actions have caused to the families of the victims. They have conducted themselves with the upmost dignity and been incredibly brave and patient throughout.
"Nothing can make up for the loss of their loved ones, but we can only hope, following today’s conviction, they feel justice has been done. Our thoughts remain with the families.”
What did the jury learn during the trial at Preston Crown Court?
A construction worker, Monaghan, of Belgrave Close, Blackburn, smothered Ruby on New Year’s Day, 2013, as she slept in her Moses basket. Monaghan was alone with the child as her mother slept upstairs at the family home.
Eight months later, after Miss Gray discovered that her boyfriend owed thousands of pounds in gambling debts, she told him the relationship was over.
The next day he took their son, Logan, aged 21 months, to a local swimming pool, Waves in Blackburn.
While alone in a cubicle in the changing rooms he smothered the child, the jury heard.
Ruby’s and Logan’s deaths were both investigated as sudden and unexplained events, but the girl’s death was attributed to bronchiolitis and Logan’s cause of death remained “unascertained”.
Both had been seen by medics in the days and months before their deaths, but other than usual childhood illnesses no serious medical condition was found.
But a review was carried out by Lancashire Police after further information came to light and Monaghan was arrested and bailed on suspicion of murder in January 2018.
As the highly complex police investigation continued, Monaghan began a “toxic” relationship with mother-of-one Evie Adams, 23, who had suffered “chronic abuse” before becoming a foster child aged 12.
Police warned her not to be with him and a court order was made banning contact.
But the relationship continued and, while on bail for the murder of his children, Monaghan killed Miss Adams after she threatened to dump him.
Monaghan told her: “I won’t keep putting up with you saying we are over.”
The defendant illegally bought strong prescription drugs on the black market via WhatsApp and other contacts.
Miss Adams was found to have tramadol, diazepam, amitriptyline, zopiclone and pregabalin medication in her body after her collapse and death on October 24, 2019.
She died from tramadol and diazepam toxicity.
He then faked a suicide note from Miss Adams, discovered apparently by chance falling out of a picture frame as he removed the couple’s favourite photo of themselves to place in her coffin.
Monaghan was re-arrested in January this year and charged with all three murders.
He claimed to have nothing to do with the death of his children, but a dozen experts told the court that while the exact cause of the deaths was difficult to pin down, imposed airway obstruction was either “likely” or could not be ruled out.
Monaghan also claimed the illegal prescription drugs were for himself and denied ever giving any to Miss Adams.