Kristoph Gavin is the real identity of the Phantom. To prove this point, let's take a look at what we know about the Phantom.
-He was stabbed in his right hand.
-He's been a spy for a decent amount of time to be considered dangerous.
-His presumed goal is to stop the Hat space missions and to prevent the truth of the past being revealed through the moon rock.
-His identity could be practically anything.
Now, let's go onto what we know of Kristoph.
-He has a wound on his right hand.
-We know very little about him and his past.
-He's practically a perfect defense attorney.
-He seeks revenge on Phoenix, even going insane over this.
-He is so skilled at suppressing his stress and emotiin that he's even nicknamed "the coolest defense in the West".
Now, let's connect these dots. We can definitely draw a connection between the scar and stabbing. But everything else is a bit more complicated. As such, I will provide a timeline of events for you.
-Kristoph becomes a spy for a reason that can be interpreted in many ways.
-He then goes on to be a perfect defense attorney, which can't be due to forging evidence, as he never met the Mishams up until this point. However, he has the help of a spy organisation, who can help him with this, most likely under the same pretense Calisto used.
-Kristoph is then given an assignment to kill Metis Cykes and dispose of the psychological analysis that could point towards his identity. By this point, Kristoph has already received his nickname and reputation, which doesn't help him hide his identity.
-He runs into Athena and gets stabbed in his right hand, which splatters blood on the moon rock. He cleans up the scene later, framing Blackquill.
-Fast-forward to the year of Zak Gramarye's trial. He enlists the help of the Mishams to forge a piece of evidence, as the spy agency was the reason he almost became suspected in the past. Therefore, he decides to use another source. This is when Vera notices his scar and the "devil" in it. He places the nail polish trap and sends the letter with the stamp as well, for insurance.
-He plays a game of poker with Zak and loses.
-Phoenix becomes Zak's attorney and Kristoh decides to frame him for the forgery. This works out very well for him, because if forgery ever came to light, he has a tangible
source to point to. A soy agency won't cut it in a court of law.
-Kristoph votes against the disbarment of Phoenix, to keep suspicion off him.
-Kristoph keeps an eye on everyone involved in the case and we jump seven years later.
-(For the sake of keeping this relevant to the Phantom, I'll assume you all know what happens in Apollo Justice)
-Kristoph breaks down in court and is taken away.
-His spy buddys break him out and keep this from being noticed because he IS a renowned spy who they need.
-His next assignment is to stall Blackquill until his execution date and find that moon rock.
-He then come across Apollo Justice, the man he had once mentored but was taken from his by Phoenix.
-He now realizes that he can pull the perfect revenge and complete his mission at the same time.
-He waits until the perfect opportunity to hit Phoenix in the personal spot, his friends.
-The opportunity presents itself at the Hat-2 launching. He proceed with his mission and murders Terran to retrieve the moon rock. But in his escape, he notices Athena in the Space Museum.
-To take revenge on her and Phoenix at the same time, he forges her prints on the lighter and waits for the perfect moment to use it.
-At the initial trial, he disposes of the rock through a bombing, to give an explanation for its disappearance.
-Phoenix takes on the case and Kristoph waits until the end to bring Phoenix's hopes up, only to present forged evidence (ironic, isn't it?)
-Fast-forward to the end of the investigation, day 2. He gets worried for a bit, because a trial is going to be forced to happen due to the hostage situation. He searches for any excuse to stop the trial and uses the "all the courtrooms are full" one.
-Phoenix surprises him by using the exploded one, which backfired on Kristoph.
-He then realizes that he can use this chance to get Athena convicted and hurt Phoenix much harder than convicting Blackquill would. He also had a personal issue with Athena, since her stabbing his hand started a series of events that ultimately made him lose to Phoenix twice, bringing him where he was now.
-This plan backfires and he's accused of being the Phantom. He hides behind his arguments, like his vast array of emotions. This, too, fails him.
-It eventually becomes too much for him and he loses his cool as he did a year prior, only this time, he's shot for it.
And that is my theory! Sorry if it's a bit long or horribly done, I haven't really presented theories in full before.

I think the reason that Meekins appeared at Edgey's even though he should've been in jail at the time was possibly because they didn't quite have enough proof,so they let him go. Then Gant used him to screw Edgey over,knowing that he wouldn't accept the report. Then the video tape was found,and THEN,in the midst of the first trial,they arrested him.