A “deceitful” and “manipulative” mother has been jailed for a minimum of 21 and a half years after murdering her seven-month-old baby and injuring another child.

Jennifer Crichton, 35, was sentenced to life imprisonment at Liverpool crown court on Wednesday.

She was found guilty of the murder of her daughter Amelia as well as three counts of causing grievous bodily harm with intent and one count of child cruelty against another child, who cannot be named for legal reasons, after a five-week trial at Preston crown court.

Crichton, of Leyland in Lancashire, had been arrested after the other child was seriously injured, years before the birth of Amelia, but was not charged until last year.

She appeared to show no emotion as she was sentenced. Mr Justice Holgate described her as “self-centred, deceitful, manipulative and lacking in any real remorse”.

He said Amelia’s death had a devastating effect on her father, Richard Sheppard – who at one point Crichton tried to blame for the death – and the rest of her family.

Holgate said: “Their pain over losing a much-loved young child and her life being so cruelly cut short will endure.”

Crichton was under a social services care plan devised by Lancashire county council and outsourced to a local social care provider at the time she attacked Amelia on 19 April.

The court heard she told a psychiatrist she had shaken Amelia three times before the baby slipped from her grasp on to a tiled floor. But Holgate said expert evidence found a fracture to the baby’s skull showed she had suffered a strike of a “violent nature”.

He said: “I’m sure that the defendant either forced Amelia down to the ground or she struck her head on to a hard surface.” Amelia also suffered bleeding to the brain and injuries caused by having been shaken in a “vigorous and violent” way, Holgate added.

Simon Jackson QC, defending, said Crichton was a “vulnerable woman unable to cope, ultimately, with the pressures of motherhood”. He said her attempt to blame Sheppard for Amelia’s injuries had been a “desperate act by a woman who couldn’t cope with what she’d done”.

Amelia was born prematurely at 24 weeks and spent six months in intensive care before going to live at home in Leyland.

She died in hospital two days after the attack.

Brett Gerrity from the Crown Prosecution Service said: “Amelia Crichton was a small, defenceless baby who suffered catastrophic injuries at the hands of her mother, who should have been caring for her and ensuring she didn’t come to any harm.

“Jennifer Crichton denied any responsibility for her death, even blaming an innocent person, until four weeks into the trial when she pleaded guilty to manslaughter. We did not accept the plea as we were satisfied that the injuries which led to her death were deliberately inflicted.

“The jury, having heard the evidence, agreed, and convicted her of murder.”