But the entire burden is on the prosecution's CIC to prove guilt.It is a standard defense technique to proffer an alternative senario and perpertrator of the crime, and thus put the seeds of reasonable doubt in the jury's mind. A defense lawyer would only propose a senario which is likely and rational based on the evidence, else it would not effectively sway the thinking of the jury.
If the SA has proof then the defense will counter it with any information that will lead to reasonable doubt. if there is no proof then the prosecution will not be able to meet the burden.