Vincent Tabak could have walked away from the attack on Joanna Yeates but instead held her by the throat long enough to "squeeze the life out of her", a court heard today.
The 33-year-old could have released his grip on the 25-year-old's throat at any time during his "protracted and persistent attack", prosecutors claimed.
During his closing speech at Bristol Crown Court, Nigel Lickley QC said that instead of walking away Tabak held her by the throat until she fell limp in his hands.
He insisted that when the Dutch engineer went to Miss Yeates's neighbouring flat on the night of December 17 last year in Clifton, Bristol - a few minutes after she had arrived home - he had sex on his mind.
Once inside her home he used his 6ft 4in frame to overpower her and to kill her as the landscape architect desperately fought for her life.
"He knew what he was doing. He was in control and he knew she would die and he held her neck long enough, and coupled with a smothering second hand, to be sure that she would," Mr Lickley told Bristol Crown Court.
"It goes to his intent and his intention to kill or cause really serious bodily harm.
"He knew she was struggling and fighting, he knew she was in pain, he knew she was frightened, he knew she couldn't breathe.
"Instead of letting go and releasing his grip and letting her live, he carried on and on and on until she went dead in his hands, her life extinguished."
During Mr Lickley's speech, Tabak did not look up from the dock, instead staring at the floor and keeping his head in his hands.
Miss Yeates's parents, David and Teresa, her brother David and her boyfriend Greg Reardon sat quietly in the front row of the public gallery. On occasions Mrs Yeates looked tearful.
Addressing the jury, Mr Lickley said Tabak had intended to kill Miss Yeates or cause her really serious harm because he gripped her throat for long enough and hard enough to end her life.
"Twenty seconds is long time," he said.
"Whatever, in fact, the period of time was - it might have been less, it might have been more, perhaps 15 seconds, 20 seconds or 30 seconds - but it is a long time when you have your hands around the throat of another person.
"It is when someone has their hands around your throat and they are squeezing and squeezing to such an extent that you cannot breathe.
"Every second means a continued determination to kill. It is long enough and hard enough, a sustained, continuous period of pressure of sufficient force to cause the body to react as it does.
"It is a long time to imagine the holding of a neck, the sounds, the fight, the fear in the eyes of the victim - all directed at Vincent Tabak.
"Because he was facing Joanna Yeates, all until the person goes limp."
Mr Lickley said strangulation brought a "unique connection" between Tabak and Miss Yeates and was not something done on the "spur of the moment".
He added: "It is not instantaneous, unlike the insertion of a knife.
"It is protracted and it is persistent and it requires quite deliberate acts and a determination to carry on and carry on despite the reaction and the actions of the victim.
"It involves a deliberate choice to rule out the decision to stop and release the grip. You carry on until the person presumably in your hand, after the person has stopped, you let them fall to the ground."
Mr Lickley rejected Tabak's claims he panicked after killing Miss Yeates and suggested he was "cool", "calculating" and "detached".
"His girlfriend had no inkling as to what he had done because he was able to mask his feelings completely," he said.
"There was no clue, no trace of emotion for her to see. There was no panic, no inner turmoil, he was cool and detached.
"There is another side to Vincent Tabak. He is dishonest, deceitful and he is a liar."
Mr Lickley also accused Tabak of making up his recollections to fit his own account of what happened inside the flat on Canynge Road and answering "can't remember" to more than 80 questions he asked him.
After Mr Lickley had finished, William Clegg QC, for Tabak, addressed the jury and said he was not going to excuse the defendant's actions and appealed to them to reach a verdict based upon the evidence alone.
"If either of us set out to win a popularity contest I would lose and rightly so," he said.
Mr Clegg called Tabak's behaviour "dreadful" and added: "But it does not alter what was in his mind at the time it happened.
"There is only one thing that I can ask and that is a verdict based on the evidence heard in this court, nothing more, nothing less."
Mr Clegg said jurors should reject the prosecution assertion that Miss Yeates's death was "planned, premeditated and sexually motivated" as the evidence did not support it.
He said the prosecution case could not explain evidentially how Tabak had got inside her flat and asked the six men and six women to accept his proposition that her death happened after 9.35pm and not shortly after arriving home.
Mr Clegg described the screams heard in Canynge Road as a "red herring" and were more likely to be students celebrating the end of term rather than Miss Yeates's desperate fight for life.
"I am going to invite you to conclude this was a very short, fast moving incident which would have been over in less than 30 seconds," Mr Clegg said.
"There was a few seconds of madness. We would invite you to say the fact he cannot provide a second by second account in what happened in that fast moving, dynamic situation is really not surprising. Could you really expect it of anyone?"
Mr Clegg concluded: "We invite you to reject the prosecution's suggestion this was planned, to reject their suggestion it was premeditated, to reject their suggestion it was sexually motivated and to reject their suggestion she was killed at about 8.40pm.
"We invite you to come to the conclusion that the evidence points to it being unplanned, unpremeditated, without sexual motivation and with death occurring after 9.35pm."
The trial was adjourned until tomorrow when the judge, Mr Justice Field, will begin summing up.