Possible motive of Hialeah teen accused of stabbing mother? Fascination with gore
Prosecutors and defense attorneys on Tuesday sparred over contested evidence in the case of the Hialeah teen who is accused of stabbing his mother to death back in 2023 — including a possible motive for the slaying.
During the hearing, prosecutors sought to bar attorneys for Derek Rosa, now 15, from pointing to alternate suspects, namely Derek’s stepfather, who they say was working as a truck driver in Georgia at the time of the murder. The state also wants to stop the defense from questioning investigators about whether they followed police procedures during the probe — and from mentioning to the jury a DNA hit that linked back to a possible relative.
But prosecutors also hinted at a possible motive: that Derek killed his mother to share photos of her slain body with his friends.
On Oct. 12, 2023, then 13-year-old Derek murdered his mother, Irina Garcia, 39, by stabbing her 46 times with a kitchen knife as she slept, while his 2-week-old sister was nearby in her crib, police and prosecutors say. While Derek confessed to the slaying, his case has received national attention due to a vocal community of supporters who believe Derek is innocent.
Prosecutor Jonathan Borst argued that Derek’s stepfather was “nowhere in the vicinity at the time of the crime,” which should limit the teen’s legal team from mentioning the stepfather as an alternate suspect in front of jurors. Borst also elaborated on a DNA hit from evidence on the scene that indicated Derek was related to a man who, in 2016, was arrested for a sexual assault.
Derek’s defense attorney Dayliset Rielo told Miami-Dade Circuit Court Judge Richard Hersch the person linked to the hit was not a known relative of Derek’s — and that she doesn’t know what the man’s whereabouts were at the time of the killing.
Rielo also said she intends to question investigators on the stand about breaches in department procedure as there is an ongoing police internal affairs investigation related to crime scene images that were shared in a WhatsApp chat.
A fascination with blood, gore
On the day of the murder, Derek showed his girlfriend a video of a man shooting himself while they were on the school bus, Borst said. The girl told investigators Derek was laughing and joking while showing her the video, leading her to break up with him. Derek had also sent the bloody video in a group chat with friends.
Borst said he seeks to introduce the evidence to show jurors Derek’s fascination with blood and gore, although Rielo argued the evidence was irrelevant. Later on the day of the murder, Derek made several Internet searches about killing, including “Where is the best place to stab someone,” “The carotid artery” and “Can a knife cut through bone,” according to prosecutors.
Less than 10 minutes after the stabbing, Derek sent photos of his mother’s body — and a selfie with his hand covered in blood — to an online friend with whom he played video games. The online friend told detectives Derek was laughing about the images. The boy said he prayed with Derek and told him to call 911 after realizing that Derek had killed his mother, prosecutors say.
A chilling confession?
Derek’s defense attorneys are also attempting to throw out statements the teen made to detectives, including a confession to Garcia’s killing. In a detailed account, Derek said he first “cut her” in the neck and stabbed where “a lot of blood sprays out,” prosecutors allege.
“I woke up, I grabbed one of the kitchen knives and I went to her room,” the teen was recorded telling a detective. “I killed her.”
Derek’s statements, Rielo said, should not be included in a trial due to his lack of maturity. Before police questioned Derek, he asked, “What is an attorney?” He also said he didn’t know his own address or phone number and struggled to read the word “coercion” while waiving his right to remain silent.
In another motion filed Monday, the teen’s lawyers accused the judge of demeaning the defense, which they say shows bias and jeopardizes Derek’s right to a fair trial. Hersch on Tuesday denied the request to disqualify himself from the case. During the hearing, Rielo said she sought to take the issue to the 3rd District Court of Appeal, although Hersch said he would not pause the upcoming trial.
The appeal has not been filed as of Tuesday afternoon, according to court records.
Hersch will rule on the other pending motions in a hearing on Jan. 5.
This story was originally published December 23, 2025 at 3:53 PM.
