That is only a thought exercise IMO, in the face of the forensic and phone evidence (no doubt there is more), and BK needs to account for his presence at the scene if the police can establish it in fact (which IMO, based on the PCA and other evidence, they could assert this at court and in interview with BK).
However, it may be possible for BK, or any defendent in a criminal case, to be found not guilty on the basis of not forming the intention to do murder, despite still committing a murder, since the law broadly requires the action AND intention. This would be the only way I believe that BK could avoid the offence.
If his defence were to argue "it wasn't him, he wasn't there at the time of the murders" or similar, I would consider that potentially an act of professional negligence on the part of his legal team, as it does not provide him with the best defence he could have against the death penalty, IMProfessionalO. It is a fanciful argument IMO, and bares no attempt to understand and refute the prosecution's case.
Edit for grammar.