At some point in Holdom's trial, the matter of motive will be referred to, perhaps, it isn't compulsory and is outside the brief of a Prosecutor, but some Prosecutors do refer to motive, sometimes in the opening address, sometimes in the summing up area of the trial.
The Defence will often point to a lack of obvious motive as a pointer to the defendants innocence.. this may be referred to many times in the defence section of the trial..
but what every human knows, there is a motive . It resides deep within the psyche of the killer, and mostly, it remains there, as motive , for a defendant is an iffy business, it can go one way or the other, and is usually best left out altogether.
Of course, Holdom may decide to persuade a jury that his motive to kill Karlie is a justifiable one.. I cant recall any time that has been a success in murder trials over many years.. it would be against his barristers advice.