Reported Theft...Can you find the thief?

CSI Lab

We were called in the investigate a reported theft. We had eight suspects, and with the evidence that was collected narrowed it down to three suspects: Mike Kelly, Ralph Johnson, and Jenny Cho.

Evidence:
1- Possibly Mike Kelly's hair (could be Jenny's)
2- Ralph Johnson's handwriting on note "I have your diamond ring"
3-Ralph Johnson's hair
4- Type A Blood Antigens
5- Mr. Kelly's fingerprint: Ulnar Loop
6- Mr. Kelly's empty wallet
7- Shoe Print

INCIDENT:
Ralph Johnson and Jenny Cho are married. They devised a plan to defraud Mike Kelly. Jenny moved in with Mike. Mike fell in love with Jenny and was going to propose to her. This was just the right time for Ralph and Jenny to inact their plan. Ralph stole Jenny's diamond ring and wrote the "I stole your diamond ring" note. Ralph came over to Mike's house to talk to Jenny when Mike wasn't home. Mike walked in on them talking and overheard part of their plan. When they realized that Mike had overheard them, they knew their plan would no longer work as smoothly as they wished. Afraid of going to jail, Ralph overpowered Mike and took his wallet. He threw the wallet to Jenny who quickly emptied it. While Jenny emptied the wallet, Mike fought with Ralph leaving some of Ralph's blood and hair behind. When the wallet was empty, Jenny and Ralph fled leaving Mike behind.