The strange relationship between mother and son Penelope and Barry Rogers, with eyewitness reports of overly close contact, leading some to believe incest was a possibility, was overshadowed by a much more sinister crime. The two planned and eventually murdered Penelope's own mother Betty Guy, intoxicating her with booze and drugs before callously smothering her. A rare case of both a mother and son involved in matricide.

• Geoffrey Wansell