The Henri van Breda murder trial turned into a science lesson in the High Court in Cape Town on Tuesday.
Mathematical formulas and Newton's laws of motion flew thick and fast as a ballistics expert and a member of the defence team got locked in a stalemate in which there was a lot of verbal force - but not much movement.
On Monday‚ ballistics expert Captain Candice Brown‚ said Van Breda's claim in his plea statement that he threw the axe used in the attacks at the alleged intruder as he fled down the stairs‚ was "possible but highly unlikely".
But on Tuesday‚ defence counsel for Van Breda - who stands accused of murdering his parents and brother in 2015 with an axe before turning on his sister who survived the ordeal - said that Brown could not have made such a statement without knowing all the different values in the formula for measuring force.
Matthys Combrink‚ for the defence‚ said: "Yesterday you were asked if it was possible the axe was thrown down the stairs. The court then asked you more specific questions focusing on different aspects of the mark on the wall on the landing‚ and you said it was possible but unlikely."
She agreed.
He added: "You did not do any experiments on this and you did not do any calculations‚ so was it just a thumbsuck?"
Brown responded that the axe-throwing theory was only put to her in the witness stand on Monday‚ and that based on the information in her official reports‚ it was not a thumbsuck.
"I looked at mark D in its entirety‚" she said‚ describing how she had looked at where it was‚ the particles of cement that landed on the staircase‚ the wall plastering that was cut through right to the brick‚ and various other data she had recorded.
Combrink asked her to share Newton's laws of motion which she had referenced on Monday.
After this‚ he said‚ "If you want to rely on these laws‚ and find out the force of the blow by measuring both mass and velocity‚ you would need to know the exact value of the mass and the velocity. You do know the mass of the axe‚ but without knowing the velocity it has no meaning in this world."
Brown responded that that was why she said it was a "possibility" rather than ruling it out completely‚ but that based on the other variations she had looked at‚ coupled with her 14 years of experience in ballistics‚ she was sticking with her statement of "possible but highly unlikely".
Earlier in the morning‚ Brown and Combrink had wrangled over another mark on the wall for one and a half hours‚ with neither conceding that the other might be correct.
Court was adjourned until after lunch.
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