Akai's fake death technique

The basic summary of the plan to fake Akai Shuuichi's death is that Mizunashi Rena will meet Akai and will pretend to shoot him. To make it look realistic, blank cartridges and blood packets with small detonators will be used. Akai will pretend to die and fall down in the truck. When Rena is fiddling with the small bomb, Akai places Kusudu Rikumichi's body in his place. He exits the truck when Kir leaves. Meanwhile Jodie Starling will have the one of Conan's two cellphones that has Rikumichi's fingerprints on it. She will think they are Akai's and when she goes to validate the identity of the body with the police, it will match Rikumichi's fingerprints and she will be fooled into thinking Akai died.

Initial Planning

After the death of Organization agent Kusudu Rikumichi, Akai Shuuichi and Conan went to talk to Mizunashi Rena after getting Hondou Eisuke to "wake her up". They speak with her about sneak her back into the Black Organization, received her promise to cooperate, and they began to formulate a plan on how to reimplant Rena without the Org rejecting her. At that point, Akai figured that the return Rena plan would make the Org's recovery of Rena seem suspiciously easy, so the Org wouldn't trust Rena and would require her to do some task to regain the boss's trust. Akai, who has experience in the Org and knows how they think, guessed the requested test of loyalty might be to kill him, so he decided to prepare appropriately to be safe. This would be the time frame when the plan to fake Akai's death was formulated.

At their disposal were three important articles: One is Rikumichi's body which be used as Akai's body double. Presumably the FBI kept the body and the car for investigation because Megure nor the news said anything about a body matching Rikumichi's description during the Shiranpuri case later. They are the homicide division, and they would probably be called to investigate any case involving a gunshot to the head, even if looked like a suicide. Akai or one of the following FBI agents either transferred the body to their vehicle or drove Rikumichi's car with the body in it to somewhere less conspicuous.
Items two and three are Conan's two identical phones, one with Rikumichi's fingerprints on it from when Conan got him to pick it up back when he was trying to determine which of the three patients was the black Organization operative. The phones will be used to trick the FBI later into thinking Rikumichi's fingerprints are Akai's.

Conan and Akai's preparations: Setting up the phone trick and Akai's body double

In the hospital during the FBI planning meeting, Akai makes a show of taking Conan's phone (not the one with Rikumichi's fingerprints) with his RIGHT hand. It has to be his right hand because that's the one Rikumichi used to handle the phone, Akai would normally handle the phone with the other hand because he is left handed. Jodie has this scene imprinted in her head. Meanwhile, Conan steals Jodie's phone and causes it to malfunction, perhaps by dropping it in water like he did to Rikumichi's, so Conan has the opportunity to loan Jodie the one with Rikumichi's fingerprints on it. Jodie will assume it was the one Akai handled and be fooled because Conan's phones are identical.
Sometime before Akai and Rena's meeting, Akai and Conan will abscond with and prepare Rikumichi's body to look somewhat like Akai. The time frame for this could be the night before the strategy meeting after the fake death plan was devised or after Rena was returned to the org but before she called to meet with Akai.

Rena and Akai's preparations: Faking the gunshots for the camera

Before Rena is returned to the Org, she and Akai discuss the timing and the location of the fake gunshots. They decide on the lung and forehead for reasons explained later. Akai prepares fake blood packets, detonators for those blood packets, a small remote to detonate them with, and protectors that go between the skin and the detonators. A setup like this already happened before back in the Kaito Kid and Black Pearl case with Suzuki's mom and the magician Sanada Kazumi, so it isn’t unprecedented. Rena takes blank cartridges, likely from the FBI, and hide them on her person since she will be under watch and may be searched by the Org. She might carry a few different calibers for different models of handguns.

Akai and Rena's meeting

Fill in Refs

With Akai, Kir, and Conan's prepwork done, the FBI plan to return Rena with the vans takes place and Rena successfully returns to the Org, and as predicted is tasked with killing Akai right away. Akai gets the expected call from Rena. He stops James Black from calling Jodie to prevent the other FBI from interfering with the plan.,
Akai heads out after loading Kusudu's body in the backseat of his truck. His model truck probably has a backseat/extended cab because it has rear side windows. Meanwhile, Conan passes the phone with Rikumichi's fingerprints off to Jodie.
At Raiha Pass, Akai scouts out ahead and drives in from the other side so the car is on the side of the guard rail that has the drop. Basically, he plans on scrambling out of the detonating truck just like Camel did earlier when returning Rena to the Org. He needs to be on the side with guard rail and the drop for it to work.

Blood packet placement and Akai's strange behavior while getting shot

When Rena goes to shoot Akai, Akai keeps his right hand in his pocket during the whole ordeal. That is unnatural, especially after having been shot once; it is more natural to have one hand cover the wound while putting the other in front of himself to protect you. Akai couldn't do that however, because he had to push the detonator for the blood packets. The shot to the head was above Akai's hat line which makes it possible for a fake blood packet to fit under there. As for the bleeding from the mouth, Akai could have bit open a small packet he was carrying inside his mouth or bit his tongue.

Disappearing blood trails indicate Akai's body was switched out

After Rena shoots Akai and he falls down in the seat, Akai's face has a blood trail running down it; later after Rena planted the bomb, the lower half of Akai's face and his body is visible, yet the blood trail is gone. This disappearing blood trail occurs both in the manga and the anime. It is unlikely to be an art mistake. There is no reason for Rena to wipe the blood off Akai's face, nor is she shown doing so. This is direct proof the body was somehow switched and there is something fishy going on.

Rena uses psychological traps to trick Gin

Rena used psychological traps to trick Gin into overlooking that she and Akai could have predicted enough details of the assassination plan to concoct a trick. Rena manipulates her conversations with Gin by suggesting possible courses of action and making requests which she already knows will definitely be rejected by him. These rejected requests subconsciously manipulate Gin into falsely assuming that Rena had wanted or planned on having things as she requested and had not anticipated his demands. The result is that Gin fallaciously believes that he was in control and Rena could not have plotted anything in advance.
The psychological trap was used when Gin told Rena how she was going to kill Akai (607). Rena suggested alternate options like Gin and company would surround Akai to shoot him, and that she would like some extra time to prepare - both requests Gin denied.
Additionally, Rena and Akai planned another psychological trap for Gin with the placement of the gunshots. Rena and Akai decided to pick a fatal- but not quickly so- lung shot for the site of the first “shot”. Rena will then say “that’s good enough, he will die quickly anyway”, but Gin will be sure to object and order her to finish him in the head where it’s certain. Rena will then deliver the coup de grâce that Gin ordered. Of course, Rena and Akai knew in advance Gin would ask for a headshot in these circumstances because that’s the kind of cautious guy Gin is. The trap is making Gin ask for the shot specifically by himself because it is hard to escape from the fallacious thought that “this couldn’t be planned in advance because I alone specifically asked Kir to shoot Akai in the head with no forewarning.”

Conveniently timed police arrive giving Akai and Kir time to complete the plan while avoiding additional scrutiny

After Rena delivers the shots, she is interrupted by police heading her way. They were probably called on purpose to force Gin to order Kir to get out of there and not examine things more closely. Kir places the bomb by the already switched body and leaves, which gives Akai a little time to maneuver without the camera watching him. He left his phone in Kusudu's pocket, and he also put the right hand of the body in the pocket as well to make sure Kusudu’s right-hand fingerprints survive and can be tested against Conan’s phone for a match later to complete the trick. The bomb has the additional effect of destroying Kusudu’s face and obscuring the powder burn from the self inflicted gunshot wound.

Conan checks his phone to see if the plan worked

After Jodie checks the body and returns a phone, Conan checks it right away. Conan notes the serial number is different which means that the police kept the original phone as evidence, and thus the plan was a success. The reason for Conan's inspection could be that should something not work out properly, the plan would change so that Rena really would kill Akai. If Akai really died, Kusudu's fingerprints on the phone would not match the dead Akai's and the police would return Conan's original phone. Conan is relieved to see the police kept his phone as evidence and gave him a new phone meaning everything did go according to plan. Later when Eisuke tells Conan "it sounds like there is a heavy atmosphere over the FBI, like someone died," Conan smiles to himself and thinks "that is OK" because Conan knows the fake death plan succeeded.

Fool your friends to fool your enemies

The reason the other FBI, including Jodie, were left out of the fake death plan is the same reason why the FBI were also left out of the plan to return Rena with the three vans. Conan, Akai, and Rena needed everyone to react realistically to Akai's death. This wound up being a good idea because Vermouth checked out Jodie and James Black, and Bourbon later investigates Jodie and Camel as well.

Problems with this theory

The gunshot in Kusuda’s body is through his temple, but when Akai “died”, he received a gunshot directly to his forehead from the center. Also Kusuda didn’t have a lung shot. (The second shot could be added later post mortem, but the coroner might be able to tell even with the burning.) Only Rena and the Org. know that Akai was shot from the front. Only the FBI, Conan, and possibly Rena if told later know that Rikumichi shot himself through the temple. If the Org. looked into the police report they might discover the discrepancy, but why should they endanger their secrecy sniffing about a police investigation when they saw the deed done before their eyes? Note that the police never mentioned any specifics about the body; they just said there were a lot of mysteries about it.

The second and perhaps more serious problem is using blanks at a close range. Although blanks lack the bullet part, the weapon will still discharge a cloud of hot gas that will burn in close range. Also, if the blank has a wad of paper or the like instead of a bullet or if there is shrapnel in the gun, it can be propelled out at high speed and be lethally driven into the body at close ranges. Akonyl pointed out that “crimped blanks” exist which lack a potentially lethal wad, but that wouldn’t do anything for the hot gas. It’s possible Gosho has ignored the actual dangers of blanks for dramatic license.