Yes, he's guilty.
Yes, he did it.
He killed three hundred people. It took just under two hours. His blood was found at the scene, under the fingernails of a victim. It was a last ditch defense, the man's nails raked at Itachi's sleeve and dug into flesh. Here are the scars on Itachi's arm to prove that it happened. He was there and he's guilty. He doesn't try to claim innocence. He did it.
He has a reason.
He will explain it. He won't be (that) annoyed to be asked. He will tell people why, if they (claim to) want to know.
It's just that no one seems to understand.
His reasons are either not normal reasons, or his emotions don't function properly. The language must not be set up for people like him, who are not like anyone else. The words don't seem to fit his thoughts. When he speaks and tries to explain, no one understands.
It's a strange thing, to have killed so many people. Maybe this is not something normal people can ever understand. Actually, Itachi knows that they don't want to understand, it comes from a part of themselves they want to disown. It's easier to see Itachi as a devil, a kind of demonic monster, a killer that was never like them and now is completely alien to them. There is nothing about him that they could ever understand, he did what they can't imagine. He killed three hundred people. He knew every one of them, either intimately or casually. They ask but they don't really want to know why.
And everyone asks anyway.
So Itachi puts neat brackets around parts of the truth and makes them sound the way people already believe. They will hear and understand an answer they already want to believe in.
He usually starts with the police's list of murder motives. Human emotions don't change, people kill over and over for the same reasons. They do it for money, for power, for honor or to cover up other crimes. They do it out of misguided idealism. They do it in fits of rage, or they do it for revenge.
He might say, for instance...
...that he did it because he hated his family.
Because he hated his clan, hated his father- the sanctimonious hypocrite, the brainless authoritarian. Hated his mother- who stood by and never interfered with anything his father did, never protected her child. Hated his grizzled clan elders, their stupid provincial ideas. Hated even his little brother, who was then just a small child. He could hate a small child because that child was one of them, because Itachi wanted to never be one of them again. He hated their lies, he hated their incestuous relationship with the Kyuubi, he hated their habit of casual fratricide- they were all killers anyway. He hated them and he killed them. He didn't regret it. He didn't think of it as a crime.
This is what he would have told the clan elders- the people who had thought summoning a demon was a good idea, the direct blood relations of others who had thought killing their friends and brothers was even better. But, as it happens, they were dead and they never asked. Too bad.
To others, he might say that he'd done it for fun.
Fun. Literally. Because he wanted to, because he had some unaddressed frustration and feelings of isolation. Because he had some untreated anger issues- would his parents have noticed? They wouldn't have cared, he was becoming exactly what they'd wanted. A connection to the rest of the village, a virtuoso killer to be pimped out for assassinations. He'd just taken his work home one day, that's all. (Whoops.)
(It was fun.) He enjoyed it. It made him feel good, because he was the classic anti-social lunatic. He wanted to do it and he had the urge. He didn't plan the murders and he didn't take precautions. He did not choose a particularly strategic night, he killed whomever got in his way. He killed a few non-Uchiha who were caught in the crosshairs. Collateral damage. Not a concern.
Being a textbook crazy, he had made no effort to cover his tracks or act innocent. His fingerprints were all over the murder weapon- and that weapon was left at the scene. He would be caught by police napping in a victim's bed. He would be traced calling the police to gloat, and doing it on his own phone line. He would answer the door to homicide detectives and the blood would still be all over his clothes. He was a criminal because he was damaged. He would be caught because criminals were sloppy. (Not his fault that the police were all dead and he walked free.)
Something like that.
This is what Itachi would have told his father.
Because his father was in love with rules.
His father was in love with textbook cases. The thing his father loved best was rules about textbook cases. In his father's eyes, killers were human garbage, they were stupid criminals, they were Social Darwinism's losers. They were easily caught in pigeonholes. Itachi feels that his father would particularly enjoy hearing that the scummy criminal in question was his son.
Or maybe he could fit himself into another kind of pigeonhole killer.
He could be the sociopath, he could be the broken human animal who was incapable of love, who's emotional brain circuits were all disarrayed. He could be the predator who saw his family and friends as soft furry prey. He could be as cold as snakeskin, as smoothly impenetrable, he could have a heart that was either fused to his backbone or lost to evolution entirely. He could have no discernable morals and no higher thought processes at all. He could have been hatched rather than born, or made- manufactured- his pieces cast in Konoha's secret ANBU prisons and glued together.
And a few of those pieces left out, a few screws loose, a few things so wrong with him that he wasn't even human anymore. This is what Orochimaru loved to see him as, this is the image that Orochimaru built his fetish on. So this is what Itachi told Orochimaru.
And Orochimaru, being further down the evolutionary scale with the reptiles, swallowed it whole.
For those who are still warm-blooded, Itachi turns to rage.
To passionate emotion. He killed in anger, he killed in a blur of fury. It was nurtured hate and it was betrayal, it was the impossible weight of the clan's secrets. It was an out of control fire, the blood boiling, it was a crime of passion.
This is a simple explanation, one that most people feel immediately. They aren't like Itachi and they understand the emotional root of murder. They don't have to have it explained in detail. Hasn't everyone wanted to strangle their family at some point? Ha ha ha. Everyone understands this.
At first Itachi had thought that Akatsuki's figurehead leader would like a mythological explanation better, maybe one involving demonic possession and the Tengu road. But Pein is a person who needs to feel that others have powerful emotions and suffer deeply. So Itachi tells him of suffering and passionate action, and Pein feels reaffirmed in his personal faith.
And the conversation ends there.
But it's not always an unpleasant conversation.
"Killed them all with your own sword, huh? How about that."
Sometimes it's just a light chat, while crossing great distances on foot.
"Three hundred people, wasn't it?"
And it's with the kind of person you'd call jolly, gregarious. The kind of person who likes to talk about unimportant things. This person puts you at ease and you don't mind the talking.
"Did you make them suffer? Ah, I know you. You did it quickly. Impatient, eh?"
Itachi does not hesitate to call a noted sadist jolly. It gets lonely out there in the empty fields and valleys, in the shadow of unfamiliar mountains and foreign lands.
"You're a funny guy, Itachi. I like you."
Itachi manages a smile and doesn't have to say anything, or explain anything. He likes Kisame too.
Madera isn't the same at all.
Though it's unwise to involve your emotions when dealing with something like Madara. (Unwise to pretend you have no emotions as well. Unwise to think that you can outfox him.)
Madara doesn't smile (his smile is another mask, another single pinhole to see through.) He doesn't chat. He has no beliefs or fetishes, and he doesn't hesitate to demand answers. Itachi knows better than to think himself wiser than a man many times his age, older than the clan itself and only alive at all due to its blackest blood magic. Madara's hand is in the murder, and he was there. But he doesn't hesitate to ask.
So Itachi did it because he snapped. (Because Madara knows an angry child when he sees one.)
Or Itachi did it because of the blood. (Killers, all of them, and made that way genetically by design. They didn't get into bed with the Kyuubi for nothing.)
Either way, simply the killer's blood and the clan's reasons- it was just the blood in him. No further explanation needed. Itachi doesn't bother to act dumb or younger than he is. Madara knows exactly what he means. .
Madara needs a warm body with Uchiha blood in it. He needs to control that body, to feel that he has a firm grip on its mind. He uses the adolescent fury or the cursed blood, and sometimes Itachi gives him both explanations. Madara doesn't care so long as Itachi obeys. And if Itachi seems out of control in some way, either emotionally or genetically. In the sword in his hand or his heart. Or both.
And Madara feels secure in his power over Itachi and doesn't ask further.
But the same cannot be said for Sasuke. Sasuke is the worst because he wants control and doesn't want it, he wants to be saved. He wants passion and disdains it. He wants hate and can't bear it.
This is all for Sasuke. This is a skill that Itachi created for Sasuke alone, for Sasuke and his question. None of it is a lie because Sasuke will hear too many lies from Madara, he will have enough lies in his head already. He will have lived his entire life for lies.
Will Sasuke be surprised? Itachi thinks of this as a present, a surprise gift, something Sasuke wants but doesn't know he wants yet. A reason and an answer.
It's something Sasuke has always wanted to know, even before it was personal to him.
"There is no reason," Itachi remembers his father grumbling. "No one wins. The victim loses their life and the killer loses their freedom. Don't look for a reason because you will never find one." This was at dinner, his father was between sips of miso, and the question was posed by Sasuke. Itachi looked over and saw his brother's small upturned face, the glittery impatience and sloppy love and sloppier resentment in the small black eyes.
The eyes are a good reason (but not the reason.)
Even when Sasuke saw them freshly dead, he wanted that reason.
And Itachi can clearly remember his tearful little voice. (Why?) It was the only thing he could say.
Whenever Sasuke reappeared, there would always be this question. In between the screaming and charging, there would be this word. (Why?) Sasuke wanted an answer and in fact he needed an answer. He would not listen to anything that suggested there was no answer.
For others it would be cut and dried. It would be a simple reason because it usually was- did Itachi do it for passion or for power? For money or revenge? To the arresting officers, it would never be complicated.
But for Sasuke it would have to be complicated. His love and his heart are getting in the way, he can't imagine his brother as a killer, so there must be another explanation. That explanation must be complex beyond words. That explanation must be given to him right now. This is what Sasuke wants more than anything, his death wish is just a pretext.
So, Itachi did it because he wants to die. (End it now.) Not by his own hand, or by that of a Konoha firing squad- no. It must be by the one. It must be by the only person he has ever cared about. It has to be Sasuke. (Be my avenger and my executioner.) Sasuke is the most precious person in the world, the only one left alive, everything Itachi has done will lead up to that moment. (Hate me, detest me, kill me.) All the pieces fall into place. This is what Sasuke wants, and what he will believe.
It would be familiar to him, it would touch his personal history. It would be in tune with the person Sasuke has in his mind already, what he sees when he looks at Itachi, when he raises his weapons to charge. Sasuke would like this reason. He would believe it because he liked it.
But maybe for Sasuke, Itachi will tell the truth.
More of the truth, since all of this is some part of the truth. An angle of the truth can be seen from the vantage point of every word he has said. But some views are better than others. For Sasuke, Itachi will say that he never wanted to do it. He was just a kid, he was in over his head. He was drawn along with forces out of his control and now it was late in the game, he was like any other criminal who just wanted a way out. No one wants this life, he'd say. No one wants to kill other people. He'd rather be caught than walk free, he'd rather die in the process, so Sasuke should get on with killing him. Sasuke should fufill his purpose now. Sasuke should end it here- Sasuke will maybe be enough like Itachi then to hear this, he will be the only one who can understand now.
This is a good reason. Itachi likes it.
He would have explained himself to Sasuke. He really would have.