4 ideas
She had spoken openly about her plans, and friends had attended dinner parties at which her intentions were discussed, yet no one warned Joe or called police in time. Singh was convicted of manslaughter on grounds of diminished responsibility and served about four years; her friend Madhavi Rao, charged as an accomplice, was acquitted.
When many people hear of a planned harm, each can treat the plan as too theatrical to be real, or as someone else's responsibility, so the warning never reaches the person in danger. Shared knowledge of a threat can make intervention less likely, because it becomes social chatter rather than an emergency that demands action.
A legal defense of diminished responsibility makes the defendant's mind the subject of the trial: her psychiatric history, disorders and inner states are examined at length. The victim, who cannot speak, shrinks to a cause of death, and his family sits in court watching the law measure the killer's suffering instead of his loss.
The law is built to establish technically defined culpability under rules of evidence. It is not built to answer the bereaved family's questions of why this happened and who is to blame. So a verdict can be procedurally correct and still leave grieving families feeling the system has betrayed them, because they wanted meaning and acknowledgment, which a court cannot deliver.