Prosecutors in the Oscar Pistorius trial on Thursday sought to show that his girlfriend was awake and ate approximately two hours before her death, which would contradict the Paralympian's version of events.
At the same time, defence witness Aina Lundgren tried to cast doubt on the state's claim, testifying under cross-examination that gastric emptying -- the speed at which the stomach digests food -- is an "inexact science".
State prosecutor Gerrie Nel alleges that Pistorius and his girlfriend argued during the night and that Steenkamp took refuge in the toilet, where she was shot dead by Pistorius. Nel claims she ate after waking at 1:00 am
Prosecution witness Gert Saayman, a forensic pathologist, told the court earlier in the trial that the athlete's girlfriend ate at about 1:00 am, roughly two hours before her death on Valentine's Day last year.
But Lundgren, an anaesthesiologist, said various factors including the stage in the menstrual cycle and diet pills can affect the speed of the process. Any attempt to determine when Steenkamp ate is "purely speculative," she said.
Lundgren said the chicken stir fry dinner that Steenkamp ate contained "insoluble fibre" -- vegetables -- that may have not been digestible.
Nel questioned Lundgren's claim, saying there was nothing about a chicken stir fry meal that would cause Steenkamp's stomach to empty at a slower rate.
Pistorius says he was in bed asleep in his upmarket Pretoria home for five hours before 29-year-old Steenkamp was killed.
The Paralympic gold medallist shot the model and law graduate four times with a nine millimetre pistol in what prosecutors charge is premeditated murder following an argument.
The 27-year-old claims he mistakenly shot Steenkamp through a locked toilet door, believing she was an intruder.
The defence is expected to conclude their case early next week, after the state has whizzed through its cross-examination of their witnesses.
In a court adjournment, Pistorius, wearing a dark grey suit, sat by his defence team, flicking through papers, and occasionally looking into the public gallery.
His sister Aimee, wearing a black blazer and white shirt, sat in silence by her brother's side.