SAN FRANCISCO (KRON) -- On Tuesday, San Francisco prosecutors showed jurors photographs of their strongest piece of evidence -- the knife that killed tech mogul Bob Lee. Their star witness, the accused killer's sister, was slated to take the stand but never testified. Nima Momeni, 40, is charged with murdering Lee on April 4, 2023 near a CalTrans yard under the Bay Bridge in San Francisco. Prosecutors say Momeni stabbed Lee in the heart because he was enraged over Lee's "inappropriate" behavior with Momeni's younger sister, Khazar. Text messages shown to the jury revealed that Momeni suspected that his sister was naked at a drug-fueled party with Lee on April 3, 2023. Bob Lee, left, and Khazar, right On Tuesday morning, Khazar showed up at the courthouse and was slated to testify on the stand. She was wearing a powder-blue silk dress and her long hair was dyed a lighter shade of blonde. Attorneys whisked Khazar up a staircase and hid her inside an unused courtroom down the hallway from the trial's courtroom. One of Momeni's defense attorneys told KRON4 in the afternoon that her highly anticipated testimony was delayed and pushed back to Wednesday.  Instead of Khazar, a Crime Scene Investigator (CSI) Unit detective for the San Francisco Police Department testified on the stand for hours about Lee's blood trail and a knife found at the crime scene. In opening statements on Monday, Assistant District Attorney Omid Talai said Momeni's DNA was found on the kitchen knife's handle and Lee's DNA was found on the blade. Talai said evidence presented at trial will show that the murder's motive was "obvious," and it centers on Khazar. "The defendant is this overprotective wannabe tough guy," Talai said. Nima Momeni walks into the courtroom in San Francisco on May 2, 2023. (Gabrielle Lurie/San Francisco Chronicle via AP, Pool) On April 3, 2023, Lee and Khazar went to a drug dealer's apartment, defense attorney Saam Zangeneh said. Khazar consumed whippets, and after Lee left her at the apartment, she consumed alcohol and GHB. Zangeneh said GHB is "the date rape drug. It's a hallucinogenic, it causes you to pass out."  Khazar became sick "to the point where Khazar is in a state of hysteria. She calls her husband and brother begging for help," Zangeneh said in opening statements. Khazar's female friend said Khazar was dressed in only a bikini and crying, court documents state.  Bob Lee’s ex-wife calls Momeni’s sister ‘the whore of high tower’: court documents Momeni picked his sister up and drove her home to Millennium Tower. Zangeneh told the jury, "you are going to see how disheveled Khazar is, she does not look OK" in surveillance videos. Khazar, center, arrives for the arraignment of Nima Momeni, her brother, at the Hall of Justice in San Francisco on May 18, 2023. (AP Photo / Godofredo A. Vásquez) https://twitter.com/AmyLarson25/status/1846259851703537797 Three witnesses have testified so far.   Witness #1: SFPD Officer Joseph Rinaldi Rinaldi was one of the first SFPD officers who responded to Main Street where Lee was found suffering from stab wounds outside Portside Apartments around 2:30 a.m. on April 4, 2023. Officers found Lee quickly because he called 911 for himself. Jurors listened on Monday to Lee's last words. Lee was recorded on the 911 call begging an emergency dispatcher for help until he collapsed on the sidewalk from blood loss.   “There was an adult male on the ground in front of 403 Main Street. He was bleeding,” Rinaldi testified. Some of the officers at the scene had their body-worn cameras activated. Photographs from the body camera were displayed for the jury showing officers standing around Lee as he was laying unconscious. Witness #2:  SFPD Sgt. Paul McIntosh On cross-examination, defense attorneys grilled Sgt. McIntosh about potentially shoddy police work. Jurors viewed surveillance videos showing two sections of Main Street near the stabbing scene. Jurors watched the videos recorded leading up to the stabbing and after. The street is mostly empty around 2:30 a.m. except for a few passing cars and a security guard. The defense attorney attempted to undermine McIntosh's police work by pointing out every car that drove by. The defense asked McIntosh if he tracked down any of the vehicles to interview the drivers about what they saw, however, police did not interview any of them. "What about that car? What about this truck?" the defense attorney asked about each vehicle driving by in the video. https://twitter.com/AmyLarson25/status/1846371052295016892 Witness #3:  SFPD CSI Unit Detective Rosalyn Check On direct examination, the prosecutor asked Det. Check when she was called to the crime scene on April 4, 2023. "It was a little after 8 a.m. We knew at that point that our victim had perished prior to our arrival. It's my crime scene. I determine who is going to take photos, take diagrams, DNA processing. The majority of the evidence started in the CalTrans parking area. The whole 400 block of Main Street was shut down... by patrol officers. Our last item of marked evidence was located in the street at 403 Main Street, the Portside Apartments." Check testified about a "blood stain drip trail" that Lee left as he stumbled down Main Street desperately looking for help. "It looked like there was one person who was bleeding," she testified. Check's testimony helped prosecutors establish that -- while Momeni is claiming self-defense -- Lee was the only person who was bleeding around the crime scene.  "I've seen a lot of blood trails," Check testified. The trail was from one victim, not two, she said.Prosecutors showed the jury photographs and videos of a blood trail stretching along a sidewalk, as well as the knife found by the beginning of the trail. In opening statements, Zangeneh said it doesn't make sense for a killer to leave a murder weapon so close to the scene of the crime. Talai told the jury that Momeni is a murderer, albeit, not a very smart murderer.  Zangeneh claimed Lee pulled out the knife. “Around 2:30 a.m., after a 90-hour drug fueled bender, Bob Lee took a knife out of his pocket … to attack Nima,” Zangeneh said. "Nima Momeni was forced to defend himself, forced to stand his ground. It’s terrible somebody’s dead, nobody likes that, but you have the right to defend yourself." Check also testified about searching Lee's hotel room at 1 Hotel on the afternoon of April 4, 2023.  "What were you looking for?" a prosecutor asked.  Check answered that the investigation was still in the "who done it" stage. The killer was at-large and unidentified. Officers went to Lee's hotel room to figure out who was hanging out with the victim. Inside Lee's hotel room, Check testified that she found an open wine bottle, wine glasses, Hangar One vodka, Don Julio tequila, and white cocaine powder on a table. Lee's luggage was still in his hotel room. Zangeneh told the jury that police also found "a huge rock of coke unused" in Lee's hotel room.  Check's testimony will resume Wednesday morning in the San Francisco Hall of Justice.