At the scene of a heinous crime,five suspects,one of whom is the guilty party,are being interrogated by a detective. Each of the suspects gives one statement and it later transpires that just three of these statements are correct.

These are the statements:

Uncle Jack: Uncle Jim committed the murder.

Aunt Mary: I did not do it.

Cousin Stewart: It was not cousin Margaret.

Uncle Jim: Uncle Jack was lying when he said I did it.

Cousin Margaret : Aunty Mary is telling the truth.

Who committed the murder?