Initially her death was thought to be a suicide, but the discovery of a scarf thrust down her throat and marks on the walls of the tunnel changed this opinion. A young man, a railway clerk who had dated Mary, had an
alibi for the time of her death.
Possible sightings A guard on the train said that he had seen a man and woman together in a
first class compartment at
East Croydon and that she matched Mary's description. He saw them again at
South Croydon railway station and at
Redhill he saw the man leave what he thought was the same compartment and exit the train. He was described as thin, with a moustache and a bowler hat, a description that didn't help identify him and he was never traced. A
signalman at
Purley Oaks said that he had seen a man and woman struggling in a first class compartment, but he hadn't attached much importance to it.
Train A 9.33 train from
London Bridge passed through the tunnel around the time of her death.
Expert witness evidence A
Home Office expert said that her injuries had been sustained before death, probably because of a violent struggle, that she had been dead approximately one hour when found and that there was no sign of sexual interference. The
autopsy showed that she had eaten a meal about three hours before her death. ==Motive==