Mia Fey
Head of her own criminal defense law firm, Mia Fey is Phoenix Wright's boss and mentor. She was a top-notch defense attorney, until she was murdered by blackmailer Redd White in the second Case of the first game. She has a younger sister, Maya, who serves as Phoenix's assistant.
Name
"Mia" was chosen to go with "Maya."
"Fey" has connections to spiritualism and magic, as it was the surname of Morgan le Fey who was a villainous magical character in the legend of King Arthur.
Background
Mia was born into a prominent family of spiritualists and was destined to become the next Master of Kurain Village. But what happened to her mother in the DL-6 Incident prompted her to leave the village to find out not only why her mother disappeared, but what happened in that incident 15 years ago.
Mia became a defense attorney working under Marvin Grossberg to learn that Redd White, CEO of Bluecorp, had leaked the information of Misty's involvement to the press, calling her a fraud.
Rookie lawyer, Mia Fey
During her time at Grossberg's law firm, she took a case in which the suspect was an escaped convict by the name of Terry Fawles, who is charged with the murder of Police Sergeant Valerie Hawthorne, who testified against him in a case five years ago, thus putting Fawles on death row. Her co-council for the trial was hot-shot lawyer, Diego Armando, coffee-maniac and a future lover of Mia's. The prosecutor for the trial was Miles Edgeworth, who happened to be new to the court system as well. During the course of the trial, Mia managed to prove that the "eyewitness" Melissa Foster was actually Dahlia Hawthorne and tried to prove that she was the real criminal, but Terry Fawles took the stand and committed suicide by drinking a vile of poison. The case had left serious scars within Mia's heart, and she never set foot into a courtroom again... until a year later...
On April 11th, 2013, Mia Fey took the case of one Phoenix Wright, charged with the murder of Doug Swallow. During the trial, Mia had not only proven Phoenix's innocence by proving that the real killer was Dahlia Hawthorne, but she also proved that she poisoned her boyfriend, Mr. Armando six months previous and that she was trying to kill Phoenix. She even had the prosecutor Winston Payne lose his hair and confidence at the end!
Three years later, Mia was rising to the top of her career, and Phoenix Wright, the young man she defended that time became her employee. Mia was Phoenix's co-council in his very first case: The First Turnabout, when he defended Larry Butz in the murder of Cindy Stone.
Mia Fey, after being murdered by Redd White
One month later, however, Mia Fey was killed by the same man who had ruined her mother's life, Redd White of Bluecorp. However, at the trial, her sister Maya channeled her spirit to help Phoenix expose White for the cold-blooded murderer he was; she even gave him a taste of his own medicine to admit his guilt.