The medium calls a spirit of someone's mother. She speaks of its name, personality, and memories. These are evidences that is the mother. A clairvoyant can say the same. The child of it cries, believing that. Is it really the mother's spirit?
 
Science has not discovered the spirit. In science, the spirit of a mother  does not exist. However, the medium claims that he can call one's mother spirit. For those who believe in her evidence, it is real. Is the spirit real or fake?
 
Identify the person in the image
Japanese has developed Incredible the radio technologies. Scientists can identify people in a picture. He emits radio waves to a photo and detects the reflected radio waves. He get the person's frequency from it. From the part that recognizes the image of the brain, he can detects the frequency of the person who sees it. Ask your Japanese friend for more information.
 
Does the medium contact with a spirit of a mother ? How to check. 
Prepare a mother's photo,  a medium, and a radio equipment
1, The researcher emits radio waves to a mother in a photo. He gets the mother's frequency.
2, A medium calls the spirit of the mother. She sees it. At that time, he examine the frequencies of her brain part which recognizes it.
3, If both frequencies is same, the spirit is the mother. If not, it is not.

This research is a failure if the medium knows the mother. Let's experiment with the spirits of people unknown to the medium. I guess that the medium rarely call the specified spirit. Ghosts appear slightly.

Summary
Almost no medium can call the spirit of the mother. In most cases it is not the specific spirit that the medium called. 

I introduced the method developed by Japanese materialists. British mediums would welcome science research. It reveals that the spirit that the medium contacts with is fake.