Poppy Widdison was fed sedatives by her mother Michala Pyke
A judge described how Michala Pyke fed her daughter, Poppy Widdison, sedatives because she was an "inconvenience" to her "squalid passion" with John Rytting.
Judge Jeremy Richardson QC told Pyke she was "utterly unfit to be a mother" and said to the pair: "You both bear huge responsibility for blighting the life of a pretty, vivacious little girl."
The judge described how Poppy was born a heroin addict and existed in a "swamp of drug addiction", and how her mother had a "deplorable attitude" towards an "innocent infant".
John Rytting who was sentenced along with Michala Pyke
Poppy died in June 2013 after suffering a cardiac arrest at Rytting's "squalid" home, in Grimsby, North East Lincolnshire, where prescription and controlled drugs were "left lying around".
A post-mortem examination could not establish a cause of death but toxicology tests carried out on her blood and hair found various drugs, and showed the young girl had been exposed to and had ingested significant amounts of heroin and methadone for a period of between two and six months before her death.
The judge described how Poppy was born a heroin addict and existed in a 'swamp of drug addiction'
David Gordon, prosecuting, told a trial that text messages between the pair discussing Poppy having a "blue Smartie" – a reference to the sedative diazapam – and going to sleep showed that Pyke viewed Poppy as an "inconvenience, who she felt was in the way with regards her relationship".
You both bear huge responsibility for blighting the life of a pretty, vivacious little girl
Judge Jeremy Richardson QC
Earlier this week, Katherine Goddard, defending Pyke, said her client faced the "realisation she has every day that ultimately she is responsible for the death of her daughter, morally, if not in law".
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Describing her client as "a damaged and troubled individual", Miss Goddard said: "Until Michala Pyke began the relationship with John Rytting, however difficult life was, Poppy was generally well cared for and those in positions of authority and responsibility were content with the levels of care she received.
The flat where Poppy was found dead
"But it was at the start of that relationship, a relationship that was toxic in every sense of the word, which brought out the worst in Michala Pyke."
In mitigation for Rytting, Timothy Roberts QC said the local drug supplier's culpability was less than Pyke's as he was only in a position of responsibility for Poppy in the last six weeks of her life, while experts claimed she had been given drugs for up to six months.
He said: "Michala Pyke had primary caring responsibility for her daughter and it's not without significance that the scientific evidence indicated that, over a six-month period, there had been an ingestion of prescribed drugs."
John Rytting and Michala Pyke outside court
But Miss Goddard said two drugs found in all sections of Poppy's hair were prescribed only to Rytting, who has a number of previous convictions, including jail sentences for burglary and grievous bodily harm with intent.
Adjourning the sentencing, Judge Jeremy Richardson QC said: "Make no mistake, the sentence in respect of each of you will be of some substance but it's important that I calibrate the sentence with some care."
He continued: "I now have a significant period of time to reflect upon the powerful submissions that have been made on your behalf."