A paedophile blamed sick online chats with a '13-year-old girl' on the stress of his dad dying from cancer.
Alex McDonald sent disgusting videos and sexually explicit photos to a person he thought was a child.
But the 19-year-old - who encouraged her to perform sex acts - was talking to an undercover police officer.
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McDonald now claims he doesn't remember the chats and denies having any sexual interest in children.
Liverpool Crown Court heard officers set up the fake profile of a girl called "Amber" on Kik Messenger.
Amber received a message from McDonald on February 9 last year.
Suzanne Payne, prosecuting, said he asked: "Do you want a tribute?"
Ms Payne explained a "tribute" was a type of sexual act a person performs and films, before sending the recording to another person.
Amber replied saying she was 13.
Ms Payne said: "He sent a video to Amber of him masturbating and a photo of his penis."
The pair exchanged Snapchat details and continued talking on there, when McDonald again sent a photo of his penis and said: "This proves it's me."
He sent another video of himself masturbating, with a sexualised message, and when she again said she was 13, McDonald lied that he was 16.
McDonald said: "Is that bad or are you fine with it?"
Amber replied "it's up to you" and he said: "I mean I'm fine with it, just making sure you're not scared."
McDonald sent her more photos of his penis; a selfie showing his face; and encouraged her to perform a sex act, before the chats ended on March 19.
Police went to his house in Plane Close, Walton on March 26, where he lived with his parents, and his mum confirmed he was the person in the selfie.
Officers seized his two iPhones and a tower computer, before he attended a voluntary police interview on September 20.
He gave a prepared statement, in which he admitted talking to Amber and accepted his actions were unlawful and he knew she was 13.
McDonald said he was "ashamed", before answering "no comment" to all further questions.
Ms Payne said examination of his phones revealed unlawful images but none related to children, for which he was not charged.
McDonald, now 20, admitted attempting to engage in sexual communication with a child, attempting to cause a child aged 13 to 15 to look at an image of sexual activity, and attempting to cause a girl aged 13 to 15 to engage in sexual activity.
David Birrell, defending, asked for full credit for his client's early guilty pleas, and said there was no actual child.
Judge Anil Murray said: "The law says I have to make a reduction for that in the guidelines and I will."
Mr Birrell told the court: "He was at a low ebb in his life at the time he committed these offences.
"He was at home, essentially isolating, caring for his terminally ill father. His father has stage four cancer, which has spread throughout his body and, frankly, he has not long left.
"He's lived beyond the prognosis he was given, which was 12 months, and the defendant was struggling emotionally and turned to alcohol.
"He sought to escape I suppose online and it was against that background that he committed these offences."
Mr Birrell said McDonald, whose mum was sitting in the public gallery, had no previous convictions.
He said: "He's from a good family who stand by him and he's fortunate that they stand by him.
"Your honour has seen the letter from his mother, she says he's a decent person, she says this is a one off, she says it's out of character.
"She refers to the stress that he was under, arising out of his father's incurable cancer. She says 'Alex is upset, distressed and remorseful'."
Mr Birrell said McDonald, who had physical and mental health issues, had since voluntarily undertaken a 'Safer Lives' course.
He said the author of a pre-sentence report believed McDonald's dad's cancer "may very well have contributed to this offending"; suggested his risk could be managed in the community; and recommended a sex offender treatment programme.
Mr Birrell suggested this "in the long run would serve to protect the public better" than a relatively short prison sentence.
Judge Murray told McDonald that in his chats with Amber, "you made it clear you weren't bothered about her being 13".
The judge said McDonald told the author of the pre-sentence report he felt "disgusted".
But he observed McDonald said he didn't remember the conversations, denied having any sexual interest in children and said he didn't think the chats were illegal at the time.
Judge Murray said: "In my judgement you're not taking ownership of your actions."
He noted McDonald had taken steps to reduce his drinking and was a paid carer for his dad.
The judge added: "You're now in a relationship with someone. I note you haven't told her about this case."
Judge Murray said McDonald was assessed as being a medium risk of causing harm to children, which "could happen at any time".
He said his mum described him as "decent and trustworthy" and a letter from Safer Lives said he had begun to understand his behaviour.
But the judge said: "I'm not convinced you're a realistic prospect of rehabilitation.
"You continue to say you can't remember what you did. You say you can't remember the conversations. You say you have no sexual interest in children.
"All of those contentions seem very unlikely to me."
He jailed McDonald for 20 months and told him to sign on the Sex Offenders Register and comply with a Sexual Harm Prevention Order for 10 years.
Children concerned about abuse can contact Childline 24/7 on 0800 1111, and adults concerned about the wellbeing of children can phone the NSPCC Helpline on 0808 8005000.
Anyone concerned about their own behaviour, or that of a family member, can contact stopitnow.org.uk and get-help.stopitnow.org.uk
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