This story was updated at 10:30 a.m. Wednesday with comments from defense attorney John Creuzot, a former judge and prosecutor running for district attorney.

A grand jury will ultimately decide whether a Dallas police officer should be charged with murder or manslaughter — or nothing at all — for killing Botham Jean in his own apartment.

But defense attorneys who've handled hundreds of murder cases say murder is the charge that best fits the case against Amber Guyger, who says she mistook Jean for an intruder.

Amber Guyger (Kaufman County Jail)

"She intended to kill the burglar," defense attorney Brad Lollar said. "Her thought process was 'I'm going to shoot the bad guy.'"

The same legal experts say critics demanding justice should be careful what they wish for because a murder case may be easier to defend.

For her part, Dallas County District Attorney Faith Johnson says her office's investigation will collect all relevant evidence for its own investigation.

"The Texas Rangers made the decision to issue an arrest warrant for manslaughter," she said Monday. "Now this case is in the hands of the Dallas County district attorney."

Johnson defended the work of the Department of Public Safety but also said that her office is in charge now and her staff will "get to the bottom of everything."

"We will make certain that justice is done in this case," she added. "The grand jury will be able to look at all aspects of this case, which will include anything from murder, manslaughter or what have you."

The officer's side

Guyger told police that she accidentally parked on the wrong floor and mistook Jean's apartment for her own.

The victim's apartment is directly above hers, on the fourth floor of the South Side Flats where they both lived.

Guyger, who was still in uniform, told investigators that the door was unlocked when she got there and she mistook Jean for a burglar when she fired her gun twice, striking Jean once in the chest.

Law enforcement is also looking into whether residents heard Guyger knocking on the door.

So why is Guyger charged with manslaughter -- not murder -- in Jean's death?

Dallas Police Chief U. Renee Hall, with State Sen. Royce West, called on the Texas Rangers to conduct an independent investigation into last week's deadly shooting. (Shaban Athuman / Staff Photographer)

When does a homicide lead to a manslaughter charge?

According to the Texas penal code, "a person commits an offense if he recklessly causes the death of an individual."

Prosecutors must prove Guyger acted recklessly to make a manslaughter case stick.

A person acts recklessly by consciously disregarding "a substantial and unjustifiable risk that the circumstances exist or the result will occur."

Longtime defense attorney Brook Busbee said the manslaughter charge doesn't fit what law enforcement said happened in Guyger's arrest warrant affidavit.

"We don't know all the facts, but the facts in the affidavit don't appear to match the manslaughter charge, because the act of shooting him wasn't reckless," Busbee said. "According to the affidavit, in her mind, it was intentional."

Defense attorney John Creuzot, a former judge and prosecutor running against Johnson for district attorney, said in similar cases, suspects are charged with murder. The Guyger case is a "deviation from the norm," he said.

"I am not aware of a case in which a person shoots another person in the torso, with death as the result, and is charged with manslaughter," Creuzot said. "In Dallas County, the longstanding practice of our law enforcement agencies, in similar cases, has been to charge suspects with murder."

When does a homicide lead to a murder charge?

If the person "intentionally or knowingly causes the death of an individual" and "intends to cause serious bodily injury and commits an act clearly dangerous to human life," according to the penal code.

If Guyger is charged with murder, prosecutors must prove she intended to cause or she knew firing her gun could cause serious bodily injury.

And murder, said Lollar, is the right charge for Guyger.

Could going to the wrong home be "reckless" if Guyger confused Jean's apartment with her own?

Botham Shem Jean (Facebook)

The term reckless only applies to firing the weapon, said Lollar, who has handled more than 400 murder cases as a private defense attorney and with the Dallas County public defender's office.

He said it's about Guyger's mental state when she pulled the trigger.

"It doesn't apply to going to the wrong apartment or not," he said. "It means when she pulled the trigger, was she reckless. Did she disregard the risk?

Judging from what Guyger told police, Lollar said, she did not act recklessly.

"If she is saying, 'The door opened, I saw a figure, I thought it was a burglar, I thought it was my house,'" Lollar said, "There is nothing reckless about pulling the trigger. She intended to pull the trigger."

Botham Jean was shot and killed inside his apartment Thursday after Dallas Officer Amber Guyger said she entered his apartment thinking it was hers at the South Side Flats in Dallas. Guyger was charged Sunday with manslaughter. (Vernon Bryant / Staff Photographer)

What defense can Guyger offer in court?

If Guyger is charged with murder, Lollar said, she could argue that she made a "mistake of fact."

With a murder charge, defense attorneys can also say Guyger was defending her property at nighttime, that she acted in self-defense and that she was stopping a burglary in progress.

All of those arguments could be couched with a main theory of a defense: that she made a "mistake of fact." She was wrong in believing there was a burglary because she said she mistook Jean's apartment for her own.

"If a jury believes she was telling truth that she was mistaken, that is an excuse under Texas law," Lollar said. "By filing a manslaughter charge instead of murder, law enforcement is depriving her of defenses she would have under a murder charge."

Creuzot said prosecutors must counter this argument and show jurors Guyger did not have a reason to fire her weapon.

"It will be incumbent on the prosecution to show that she did not have justification such as the use of deadly force for self-defense, or deadly force to prevent the other's imminent commission of arson, burglary, robbery, aggravated robbery, or theft during the nighttime or criminal mischief during the nighttime," Creuzot said.

Lollar said that, in theory, Guyger could testify at a manslaughter trial and tell jurors that she did not act recklessly, she acted intentionally. He said that could lead to an acquittal if she is ultimately charged with manslaughter.

What punishment does she face?

Murder is punishable by five years to life in prison.

Manslaughter convictions carry a punishment range of two to 20 years in prison.