South African athlete Oscar Pistorius has been accused of being a "deceitful witness" who dropped the "baton of truth", at the start of closing arguments in his trial for murder.
Prosecutor Gerrie Nel began his concluding remarks on Thursday, with the defence due to follow on Friday.
Mr Pistorius denies murdering his girlfriend Reeva Steenkamp.
He says he mistook her for an intruder, but the prosecution says he deliberately shot her after a row.
Ms Steenkamp was killed at Mr Pistorius' home in South Africa's capital, Pretoria, on 14 February last year.
The long-running trial was adjourned last month ahead of closing arguments.
At the court in Pretoria, Mr Nel began his closing argument by accusing the athlete's lawyers of presenting two lines of defence that "can never be reconciled".
Mr Pistorius said he had fired both involuntarily and also out of fear, Mr Nel argued, insisting the court had to choose only one of his defences.
He said the court "should have no difficulty in rejecting" the athlete's version of events because it was "devoid of any truth".
He also attacked Mr Pistorius for presenting himself as "a victim of circumstance."
Mr Pistorius' estranged father, Henke, was in the packed courtroom for the first time during the trial. It was also the first time that Barry Steenkamp, Reeva's father, had attended.
The BBC's Africa correspondent, Andrew Harding, says Mr Nel will explain in detail during his remarks why he believes he has proved that Mr Pistorius deliberately murdered his girlfriend.
The evidence of neighbours and forensic experts will be important - but the athlete's own testimony is crucial, our correspondent says.
The prosecution is convinced he gave conflicting accounts of how and why the double amputee shot Ms Steenkamp four times through his toilet door.
Judge Thokozile Masipa - a subdued presence so far - is now likely to intervene more and her questions could well provide hints about a future verdict.
Oscar Pistorius's lawyer, Barry Roux, will give his closing remarks after Mr Nel, in what correspondents say is the final showdown between two of South Africa's top legal minds.
Judge Masipa is expected to adjourn the trial after hearing the arguments to consider her ruling, a process that analysts say will take in between a week to a month.
There is no jury.
If found guilty of murder, the 27-year-old, who went on trial on 3 March, could face life imprisonment.
If he is acquitted of that charge, the court will consider an alternative charge of culpable homicide, for which he could - if convicted - receive about 15 years in prison.