Ceon Broughton, 29, denies the manslaughter of girlfriend Louella Fletcher-Michie, 24, at Bestival on September 10, 2017.
Prosecutors have accused him of letting her die after giving her a “bumped up” hit of 2-CP.
Corrie daughter Louella was left hallucinating and shrieking as she succumbed to the drug just a short distant from the medical tent at Bestival.
Broughton also denies supplying her with drug which led to her overdose in 2017.
Louella’s family were in the public gallery to hear his explanation for the very first time, at Winchester Crown Court.
“It may be tempting to point the moral finger, but that is not what you must do.”
Stephen Kamlish QC
Broughton has not given evidence throughout the trial so his QC Stephen Kamlish’s closing speech was the first time the defence has been heard.
He said: “This is case is not about moral responsibility, it’s about criminal responsibility.
“It’s not a case about vengeance although there is a temptation to think someone has to pay.
“It’s not about giving the family something that can ease their pain – nothing can or will do that.“
Mr Kamlish went on: “He did not mean Louella either to suffer or die. We all feel cheated by him not getting into the witness box.
“Everyone was waiting for him to give his side of the story.
“He could have got into the witness box and he could have cried, as he has done quietly throughout this trial.
“He could have said sorry, with hindsight of course he is sorry. But how much could he have actually helped you with the facts. For the most part, you know it all already.
“His girlfriend, someone he loved, she certainly did him, he would have done more if he thought it was the right thing to do.”
Broughton took a series of videos Louella as she succumbed to the drug instead of getting for help, the prosecution say.
Video shows her laying lifeless in the undergrowth with bloodied hands – with recordings also show her yelling for her mum and dad.
Clips shown to the court showed her apparently so confused she is trying to eat thorns and hitting and slapping herself.
He is also accused of taking a picture of her after she died around 11pm.
Kamlish added: “People who live a certain life film everything they do – for the Instagram, for the snapchat. It’s the way they live.”
Broughton allegedly refused to get help because he feared cops would catch him with drug while he was serving a suspended sentence, the prosecution say.
Louella’s TV star dad John previously broke down the dock while reliving the night she died, saying “How could say you love someone who you left to die in front of you?”.
Prosecutors have also claimed Louella had a 90% chance of survival had Broughton gone and got help – but the defence have said she took almost six times accepted dose and could not have been saved.
The trial continues.