The women were killed by Julie’s nephew, Christopher Whelan, 21, who was jailed for life with a 15-year minimum term after admitting two counts of manslaughter on the grounds of diminished responsibility.
A week-long inquest at Chesterfield Coroner's Court concluded Liam intended to take his own life when he died.
After finding his mum drowned in a bathtub and his grandmother strangled, he made an anguished 999 call to raise the alarm.
He then spent 13 hours at a police station as a ‘significant witness’, where his clothes, shoes and phone were taken for forensic examination.
Detective Constable Michael Wallis said: “Liam wasn’t happy about it but he understood.”
The jury heard Liam had suffered with depression from an early age.
The day before his death, he was arrested and questioned by Derbyshire Police over allegations of possessing indecent images and possession of cannabis.
On the day he was released, he accessed the train tracks in Shirebrook where he took his life.
A note was found in his pocket.
The jury concluded ‘nobody involved before or after his release had any causes for concern regarding his safety’.
While in custody, risk assessments were carried out in line with guidance in place in 2016.
However, neither the officers involved with the case or Liam’s solicitor were aware of these new processes.
The jury concluded the time and place of the risk assessments being carried out following Liam’s interview was not ideal.
The jury entered a conclusion of suicide, ruling: “There was no evidence any single factor contributed more significantly than others to Liam’s decision.”