The investigation into an 18-year-old’s death from a suspected overdose, which led to three arrests, enters its next phase with a judge referring charges to a grand jury.

Brayan Torres, Mut Khan and Reath Khan appeared together Wednesday in Warren District Court for a preliminary hearing in their criminal cases.

Torres, 19, of Bowling Green, is charged with reckless homicide and first-degree trafficking in a controlled substance (fentanyl), both in connection with the Jan. 21 death of 18-year-old Acacia Rose Martinez.

Torres, Mut Khan, 28, and Reath Khan, 23, are all charged with engaging in organized crime and first-degree trafficking in a controlled substance, based on allegations that the three were involved in a conspiracy to deal fentanyl, a synthetic controlled substance that can be lethal in small doses.

Detective Kyle Laing of the Bowling Green-Warren County Drug Task Force testified Wednesday about the investigation, saying in court that Torres was developed as a suspect in connection with the death through phone forensics and other methods.

Laing said that police believe that, in the hours before she died, Martinez and Torres spent a substantial amount of time together before she traveled home.

Police intelligence implicated Torres in the use and distribution of fentanyl, leading Laing to conduct surveillance on Torres’ residence.

On Jan. 31, Torres was seen leaving his residence and getting into a silver vehicle parked in the driveway and sitting in it for less than a minute.

Laing said that he used his police radio to notify other detective to converge on the vehicle, and as Torres exited the vehicle he was ordered to the ground and detained.

The driver of the vehicle was identified as Reath Khan, and detectives recovered a package weighing about 2.4 grams of suspected fentanyl in a plastic baggie wrapped within a Post-it note, Laing said.

Police also recovered a handgun from the vehicle and a hotel room key card from Khan.

When detectives went to the hotel room at Intown Suites, they encountered Reath Khan’s brother, Mut Khan, who was arrested on unrelated warrants.

Mut Khan declined consent to have the room searched, but when he asked to retrieve a sweatshirt from the room to put on before being taken into custody, officers escorted him into the room and saw drug paraphernalia in plain sight, Laing testified.

“(Mut) Khan made the statement that anything we found in the room belonged to him and he would take the charge for it,” Laing said.

After obtaining a search warrant, police recovered about 8.5 grams of suspected fentanyl, more than $1,000, about 2.4 grams of suspected crack cocaine and about a pound of marijuana from the room, Laing said.

Reath Khan faces a charge of convicted felon in possession of a handgun, while Mut Khan was also charged with possession of drug paraphernalia and intimidating a participant in the legal process.

Laing said that the intimidation charge stemmed from a deputy jailer overhearing a statement Mut Khan is alleged to have made to his brother while in custody at Warren County Regional Jail.

“As the officer walked past he overheard (Mut Khan) say ‘when I get released I’m going to look up everyone’s family involved in arresting me and find out where they live,’ ” Laing said.

Laing said that officers found communications between Reath Khan and Torres on phones recovered during the investigation, that the packaging of the suspected fentanyl found in the hotel room matched what was found in Torres’ possession and that organized crime charges were returned against the three men based in part on those communications as well as Mut Khan implicating himself to officers.

The detective testified that while the hotel room was registered in Reath Khan’s name, the amount of clothing seen in the room suggested that both brothers were staying there.