Doctors have been warned not to dismiss the possibility of foul play in cases of sudden infant death, even if the parents display intense love and grief. The warning has come after a woman who killed three children managed to convince the authorities that they had died naturally.

It took three murders and two attempted murders for the woman (referred to as M) to be convicted—the delay perhaps resulting from the fact that doctors could not accept that someone who could grieve so deeply was capable of …