A mother and father have been jailed following the death of their eight-day-old daughter.
David Nolan, 30, and Sophie Nash, 31, were found guilty of causing or allowing injuries that led to the death of Ava Grace.
Officers were called to their home after baby Ava was reported to be unresponsive on 16 August 2017. She was taken to Royal Blackburn Hospital, where she died a short time later.
A post-mortem revealed Ava died of a catastrophic head injury, likely to have been caused by forceful shaking.
Further investigation also found the newborn had also suffered a separate brain injury, as well as a broken leg, which she is believed to have suffered in the days leading up to her death.
Following a trial at Preston Crown Court Nolan was jailed for 10 years, while Nash was handed eight years in prison.
Speaking after the couple's conviction, the officer who lead the investigation, Detective Chief Inspector Jill Johnston from Lancashire’s Force Major Investigation Team, said throughout the complex investigation, neither parent had ever "accepted responsibility for harming Ava", with both Nolan and Nash blaming each other.
She added: "Whilst we have been unable to prove which one inflicted those horrendous injuries which caused their baby daughter’s death, what we have been able to prove is that they are both ultimately responsible.
"One of them shook baby Ava to death and the other allowed it to happen.
"Neither of them sought medical assistance for the initial injuries that Ava suffered in those very short days of her life and I suspect that they delayed seeking medical help on the evening of her death, until it was certainly too late.
"Nolan and Nash were blessed with a healthy baby girl, a newborn baby who they should have loved, cared for and protected from harm.
"To think that they are responsible for her death is inconceivable.
"The couple admitted having an extremely volatile and violent relationship, exposing baby Ava to considerable risk, which ultimately proved fatal.
"Whilst we cannot change the events that took place we have continued to seek justice for baby Ava."
A police investigation found both Nolan and Nash denied access to a number of agencies including Social Services, midwives and health visitors following Ava's birth.
Despite healthcare professionals eventually undertaking a "successful visit" they were, Det Ch Insp Jill Johnston said unable to "have ever predicted the levels of violence that this couple would go on to inflict on their baby."