An Exeter University expert on Agatha Christie has taken part in a project to solve the mystery of how she constantly keeps her readers guessing.
The works of the world's most popular crime novels have been analysed by a team including Dr Jamie Berntal.
They found that the killers are always introduced early in the book - and that female murderers are often discovered through a domestic item.
Modes of transport that feature in the story can also provide a clue - land-based transport such as cars and trains point to a female killer, while ships and planes can indicate that it's a man who 'dunnit'.
Re-elected PCC to prioritise ‘limbo’ chief constable situation
Exeter Cathedral abseil raises over £50,000
Moves made to avoid controversial estate management firms
Turnout for police and crime commissioner election drops as count continues
How Exeter's traffic troubles influenced council vote
Alison Hernandez secures third term as police and crime commissioner
