I disagree. I don't believe anyone on a jury would be willing to wink at BM's murder of SM. BM's knowledge that SM committed adultery is not a good reason to kill his spouse of 26 years and the mother of his two children. There are no good reasons to murder your spouse. The solution for unfaithfulness in marriage is divorce, not murder. Only a monster would think otherwise, IMO.
I am saying the defence is giving a wink to the jury
i.e. being realistic, even a juror with sympathy for the defence case, is likely to be troubled by the accused's highly suspicious behaviour. The defence cannot acknowledge that out loud, but must be aware of it.
This is why IE stresses so much that the accused has been badly treated. She's is providing the rationalisation to acquit, even if you think he likely did it.