Welcome to homicide school—a sort of real-life CSI training for Los Angeles investigators, taking place this week at the Residence Inn in South L.A. County.

While these scenes of horror weren't exactly real—the blood was fake and the props could have been found on a Quentin Tarantino set—the grisly tableaus came close. They were drawn from actual murder cases, such as the case of Cocaine Katie, in Room 411.

The two-week homicide course teaches newbie detectives about the latest crime-scene technology, and what to expect in their first encounter with the dead. Taking place four times a year, in nondescript hotels such as this, the training allows young detectives to sniff around crime scenes under the watchful eye of more experienced colleagues, such as Sgt. Richard Longshore, a cold-case detective with the Los Angeles County Sheriff's Department.

“We'll only get one bite at this apple,” said Longshore, a 40-year veteran cop who has investigated such cases as the alleged “Westside Rapist” serial killer John Floyd Thomas, killer photographer William Bradford, and former security guard Raymond Lee Jennings, who killed an 18-year-old girl at a Palmdale park-and-ride lot in February 2000. “Defense attorneys will have eight to 10 years to destroy the homicide report you wrote in four hours.”

On a recent, very hot California afternoon, five teams of detectives combed through the hotel and its crime scenes, looking for clues, interviewing witnesses, and gathering evidence—including cigarette butts, bullet casings, fake movie blood, and vomit made from cream of chicken soup.

During the course, given by the state Commission on Peace Officer Standards and Training to set minimum training standards for California police officers, seasoned homicide detectives critiqued younger investigators, evaluating their skills in finding clues and crime-scene evidence.

Around the hotel, signs read: Law Enforcement Training in Progress.

“The goal is to prevent and correct mistakes during the handling and collection of evidence so it can't be used against you later in court,” Longshore said.

In Room 411, detectives scoured the room and, after a while, discovered a notepad with a page missing. The writing impression was still visible on the pad. The detectives—a couple of tough-looking younger cops—quickly realized this was a clue: The killer had made flight plans, and jotted them down on the pad, before tearing the page off. Luckily, the impression he made in ink was visible on the page beneath—a telephone book, open to a page with airline numbers, seemed to corroborate the findings.

But, as Martin Rodriguez, one of the instructors, said: “A good homicide investigator will not jump to conclusions.” The purpose of the exercise, he said, was to “document a scene, locate evidence, and gather enough evidence to continue your investigation.”

Cocaine Katie wasn't an actual person. Rather, the crime scene in Room 411 was a composite of different cases, involving various murdered women. In some of the cases, police were able to make arrests; in others, they weren't.

The story behind the dead man in the bathtub in Room 626 was also likely drug-related, although police didn't find any witnesses and were unable to discern a motive. But because of the viciousness of the attack, and its circumstances, investigators believed it to be the work of a Mexican drug cartel, known to torture its victims, going so far as chopping off their heads and dumping the bodies in barrels of lime. One man was arrested but never charged.

Longshore recalled the cocaine wars of his era—the mid-1980s, when rival cartels were involved in bloody turf wars that made their way into Los Angeles. “This is much more vicious,” he said. “They aren't hesitant about chopping off limbs. We need the young detectives [to be] aware of this.”

Outside, detectives gingerly placed blue crime-scene markers next to a 40-ounce bottle of tequila, a teddy bear, a pick and a shovel. In real life, a San Dimas sheriff's patrol unit detained a mother, a father, and their teenage son as they walked out of the Angeles National Forest, carrying a pick and a shovel. Deputies searched the area and found the shallow graves containing two dead children—a badly beaten young boy and the remains of an infant. The parents were later charged with their children's murder.

Longshore has seen it all—a suicide victim whose gang name was tattooed on his penis; a pedophile who killed a mother and father so he could rape, torture and kill their 8-year-old daughter; a young Hollywood starlet who died of hypothermia after her friends put her in a bathtub full of frozen bags of peas instead of taking her to the emergency room when she overdosed on heroin—and still believes in the importance of what he teaches. “Working homicide is more of a calling than an assignment,” he said, matter-of-factly. “It will change you as an individual. You will see more things than an individual is meant to see.”

And in the end, he said, it's the little things that cops can do that make the biggest difference— for better or worse, like failing to note environmental conditions or contaminating the scene. Most importantly, he said, detectives need to keep the press informed because “if you don't, a reporter will find a dumb cluck on the sidewalk that will color the story.”

Christine Pelisek is a reporter at the LA Weekly, where she has been covering crime for the last five years. In 2008, she won three Los Angeles Press Club awards, one for her investigative story on the Grim Sleeper.