He said that the result of the black talon bullet on her arm caused an 'instant amputation.'
The Black Talon bullets open up on impact, creating six sharp 'talons.' Earlier in the trial ballistics expert Captain Christian Mangena explained that these talons 'cut through the organs of a human being.'
Reeva's mother, June Steenkamp, was also in court this morning to hear the evidence.
Mr Dixon disagreed with an earlier assertion that Reeva was hit in the hip first, with the second shot missing and last two hitting her in the arm and head.
He said that he believed the first two shots hit Steenkamp in the hip and arm while she was close to the door. He also suggested her right arm may have been stretched out towards the handle of the door, trying to open it - supposedly suggesting that she was not trying to hide from Pistorius.
Dixon, a witness for the defence, is one of about 14 to 17 witnesses scheduled to come to the stand.
This morning the judge also confirmed that there would be a two week adjournment after tomorrow, until May 5. So far the trial has lasted 7 weeks.
The Paralympic athlete, who is charged with premeditated murder, claims that he opened fire through the closed bathroom door because he feared an intruder was in the house. Only later realising he has shot his girlfriend.
But prosecutor Gerrie Nel has accused the Bladerunner of constantly tailoring his evidence as the trial goes on, and that there are significant discrepancies in his story.