From the National Records of Scotland -
William Martin , not married , Age 23 , collier, Address Whitletts Toll, St Quivox, Ayr
Victim Mary Bryce or Bryson , wife of Thomas Byrce or Bryson, No fixed residence but temporarily living with in Alloway Street, Ayr.
There is another record for the trial - AD14/49/110
Accused- William Martin, not married , not called.
If he was not convicted perhaps that could be a reason for changing his surname
Maybe not ?
JC26/1849/421 William Martin, not married, Verdict guilty, sentence: transportation - life
ev