A murder accused teen was too "pre-occupied" with her phone to play a part in the savage killing of a frail and vulnerable Hartlepool woman, a court heard.
Jurors were told that the younger of two girls who allegedly battered Angela Wrightson to death in her home in Stephen Street in December 2014 was conducting conversations with a number of people while her co-accused went "bezerk" and launched a frenzied assault.
John Elvidge QC, who defends the younger girl, said she is "simply not guilty" of the murder - and that her phone is her "alibi".
The two girls, who 13 and 14 at the time of Ms Wrightson's death, both deny murder.
Mr Elvidge QC told the jury in his closing address that the older girl attacked the 39-year-old after a fall-out and that she acted alone.
He said that between the hours of 8pm and 11pm - when the prosecution say violence is believed to have erupted - the younger girl spent much of her time sending and replying to text messages and answering a phone call.
Both were at Angela Wrightson's home at the time after calling on her earlier in the evening to ask her to buy alcohol for them.
Mr Elvidge QC said it was 'absurd' to suggest she broke away from her conversations to help "duff up" the victim.
Mr Elvidge QC said: "Between 8pm and 9pm, (the younger girl) was on the phone quite a bit.
"We suggest she is one of those people who are pretty compulsive in their use of their phone.
"You might have formed the view such people are indifferent to what is happening to them and around them.
"She is a compulsive phone user, an ego-centric teenager maintaining a series of conversations with different people, while in any view, mayhem is going on around her."
Jurors heard that during this period, the defendant was exchanging messages with at least five people, with subjects ranging from organising a party to bickering with a friend.
Mr Elvidge QC said: "It would be surprising if someone could coolly multi-task, carrying out conversations while at the same time duffing up Angela Wrightson."
The court heard the flood of messages continued to flow from 10pm until 11pm, with the girl replying to messages in a 'coherent' manner.
Mr Elvidge QC added: "The telephone usage shows that during the first visit to Angela Wrightson's house, (younger girl) was not a raging monster, was not out of control.
"She was pre-occupied by her phone, maintaining conversations with different people on different topics at that time.
"The idea that she broke away from her phone for a few minutes before joining in battering Angela Wrightson and trashing her home before returning to sending nice messages is absurd.
"The inconvenient truth is that (older girl) goes bezerk all by herself and didn't need any help from (younger girl) who was otherwise engaged.
"An alibi usually means being in a different place altogether but, in a funny sort of way, her alibi is her phone."
Mr Elvidge said there is no scientific evidence to prove that the younger girl took part in the attack.
He reminded the jury that evidence earlier in the case from forensic scientist Dr Gemma Escott revealed found that the girl's finger prints were not found on potential weapons found in the house or on the blood-spattered wall of the living room, where a handprint of co-accused was discovered.
He said the younger girl's decision to ring first for a taxi and then to call police for a lift home from the very street the victim had been attacked does not suggest a 'guilty mind'.
He argued if she believed she may find herself in serious trouble, why would she take a Snapchat picture from the police van.
Mr Elvidge added: "They get in the police van and (younger girl), who is supposed to be intelligent or bright according to others, takes a picture in the van.
"It doesn't suggest she had a guilty mind or is someone fearful of apprehension.
He said witness from a friend of the defendant who stated she called her on the evening of the attack and heard her encourage her co-accused to continue the beating was 'unreliable'.
He said that as the witness told the jury the defendant had allegedly told her co-accused to either 'bray' or smash' Angela's head - but could not be sure which terminology was used - the evidence could not be relied upon.
He said that evidence that the girl had confided in another friends that she had joined in the assault was 'bravado' on her part and an attempt to 'big herself up'.
Concluding his case, Mr Elvidge argued that the jury should return a verdict of not guilty to murder if they couldn't be certain the girl played a role in the violence.
Mr Elvidge QC said: "If you can't be sure that she played a part in the unlawful killing of Angela Wrightson, you should return a verdict of not guilty."