This item was omitted from the trial, not because of the alibi plan, but because it involved a different kind of crime and a defendant's previous criminal activity (even if just fantasy) can be suppressed.  The judge ruled that it had relevance but the Defence fought very hard to get it omitted.

Mark Buckley, a friend of David reports an incident 4 years prior to the murder of the Bain family in which David related a fantasy he had of committing some kind of act while on his paper run.  This plan included written notes.  The very same alibi was used in the Bain family murder trial whereby David used his paper run as an alibi.  This plan involved starting half an hour earlier, doing part of his paper run, then doing the crime, before doing the rest of his paper run while making himself conspicuous to as many people as possible.

This evidence is supported by another witness, Gareth Taylor, who was privy to a similar conversation but cut it short before too much detail was revealed.

Both of these testimonies can be seen on video HERE and NZ Herald HERE

Reasons why this and other evidence was omitted can be viewed in pre-trial transcripts

Law professor surprised this evidence was suppressed.

An Otago law professor Kevin Dawkins is surprised direct evidence alleging David Bain had plans to use his paper round as an alibi for committing a crime was not allowed to go before the jury when evidence verging on hearsay and detrimental to Robin and Laniet Bain was.

"It raises a question about how the defense led a wide range of evidence about four people who could not answer for themselves, yet a direct witness made a statement that was excluded," criminal law professor Kevin Dawkins said.