Although Penny Jackson openly confessed to police to brutally stabbing her husband to death in the kitchen of their family home, she claimed she only did so after having been pushed to her limit by a sustained campaign of abuse. It’s a claim vigorously disputed by the prosecution and by David Jackson’s sister, Jenny. But support for David’s aggressive tendencies comes from an unlikely source, who was never called to testify at trial – David Jackson’s estranged brother, Alan.