The suspect was caught two blocks from the scene. The gun was inside his backpack. Multiple witnesses identified the shooter who tried to kill a man on a Brooklyn street.

It was an open and shut case — until it got to the jury.

“We caught the guy dead to rights, and the jury said, ‘Why didn’t you guys do DNA?’ ” recalled the former assistant district attorney who handled the case.

That testing for DNA is rare, time-consuming and expensive, particularly in such a straightforward investigation, didn’t register with those sitting in judgement. The man was acquitted of attempted murder, and even gun possession.

“It’s not a whodunit. We caught him with the gun, with the same outfit. Multiple witnesses said, ‘That’s him,’ ” the frustrated attorney said. “Everybody expects there should be DNA on everything. Everybody expects that we have this super lab somewhere that does all this stuff.”

Making science cool



Everybody thinks that thanks to one particular pop-culture phenomenon: “CSI: Crime Scene Investigation.” Premiering in 2000, “CSI” was once one of the most popular shows on television, watched by more than 26 million people a week. The series ends tonight on CBS with a two-hour movie.

Anthony E. Zuiker, who created the show, was inspired by watching a series about forensic science on the Discovery Channel. It featured the murder of Linda Sobek, a former Los Angeles Raiders cheerleader who was killed by a photographer.

“When they pulled that long, blond hair follicle out of the headrest of the passenger’s side, it suggested that her hair was yanked out in some sort of a struggle,” Zuiker told Ad Week.

“It was really at that defining moment that I understood that the body was the perfect specimen for crime solving. And that gave me the inspiration to go below the tape with a forensic police drama and take a forensic point of view.”

Zuiker would tell the AP that his goal was to “make science cool and fun for America.”

Problem is, “CSI” made things too cool. It often featured technology that was on the cutting edge of forensic science, innovations unavailable to the average police department — and even untested. And even when it showed things that could be done, the show, and its countless spinoffs and copycats, was unrealistic about how many resources can go into investigating the average crime.

“Jurors know more about the types of testing that in theory, can be done, but they certainly don’t know when it’s appropriate to use those types of tests,” said former Manhattan Assistant District Attorney Jordan Arnold, now of the investigative firm K2 Intelligence.

“Has it taken us from this place where jurors expect more than proof beyond a reasonable doubt, and instead, demand proof beyond any doubt?”

Expecting it all



Defense lawyer Norman Steiner has seen the way “CSI” has changed criminal courtrooms.

“I remember back to the ’90s when we were doing a lot of buy and bust cases,” he said. The defense would always ask why law enforcement hadn’t looked for fingerprints on the plastic bags containing drugs, but “it never worked back then. Half the judges would sort of make a face when you were making the argument. They were like, ‘You’re crazy, no one’s going to do that on a drug case.’ The only time fingerprinting occurred was on burglary and in homicide cases, and jurors were fine with it.”

Now, Steiner said, half a prosecutor’s speech to prospective jurors explains how they “really don’t have ‘CSI’-type evidence, and ‘this isn’t ‘CSI,’ ” he said.

On drug cases in particular, juries sometimes reject logic in favor of some kind of technological evidence, says New York City’s Special Narcotics Prosecutor, Bridget Brennan.

Some cases simply don’t require expensive forensic science or high- tech TV wizardry, where show after show has a security camera on every block ready to catch footage of a crime, or a super-convenient database full of handy information, or lab results that are back in the blink of an eye, Brennan said.

“Jurors should want certainty, I think that’s a good thing. They just have to understand, there are limitations. We don’t have a database with everyone in the city in it and the car they drive and their fingerprints,” she said. “And if we did, many civil libertarians would object to that.”

A 2012 case handled by Brennan’s office shows just how far the obsession with forensic science can infiltrate the courtroom.

Investigators spotted a drug deal between a man and a woman go down in a Bedford-Stuyvesant car, but when they tried to slap the cuffs on the driver, all hell broke loose, said Kati Cornell, a spokeswoman for Brennan’s office.

“He began wildly swinging his arms, kicking his legs, throwing his elbows and attempting to tackle the officers,” she said.

The fight at Hancock Street and Malcolm X Boulevard drew a crowd, especially when the man’s pants fell down, Cornell said. By the time the wild melee was over, investigators found a softball-sized bag on the ground next to where they’d been wrestling with the suspect. The bag had 31 rocks of crack cocaine and 12 baggies of the drug inside.

The driver had been arrested in a different drug case just six days earlier, and had past convictions for drug and weapons possession, but jurors cleared him of the top charge of third degree drug possession with intent to sell in the June 2012 case — because the investigators who tangled with the unruly man couldn’t testify they’d seen the drugs fall out of his pockets.

Instead, he was convicted only of resisting arrest, a misdemeanor that carries a sentence of up to a year in jail. The top charge would have carried more time.

“After the trial, the attorneys spoke with the jurors, and they said there should have been DNA evidence recovered with the crack cocaine and that was why they acquitted,” Cornell said.

Usually, jurors get it right, added Brennan, but shows like “CSI” are so pervasive, it can give a prosecutor pause.

“You’ve got to hope that there’s a juror who’s sitting there saying, ‘Oh come on, you can’t believe everything you see on TV,’ ” she said.

Mistakes can be made



Television has always had some influence on the legal system, lawyer Robert Tolchin said.

“Lawyers used to do summations that went on for an hour, and then, ‘LA Law’ came on,” he said, noting that summations got a lot shorter once the show became popular.

But “CSI” has affected courtrooms more than any other, because it’s popularized the idea that DNA is everywhere — and infallible.

“It’s kind of the idea that ‘CSI’ is the easy way, in which it works every week,” said lawyer Barry Scheck, director of the Innocence Project.

The show is limited only by imagination, not reality, so there are “all kinds of techniques that haven’t been validated, and some that haven’t been invented yet,” he said.

For instance, bite marks haven’t been proven as a foolproof method of identification. “There are serious problems . . . in terms of scientific validation and the actual implementation of these methods,” Scheck said.

Even those accused of crimes don’t always realize TV science doesn’t measure up to real life, said criminal defense lawyer Melanie Marmer, a former prosecutor.

“The clients ask you, ‘Why can’t they check my fingerprints and see that I was never there?’ . . . They don’t go around and fingerprint the whole place to see if you were there. They just don’t do that in real life,” she said. “Or, ‘Didn’t they fingerprint the gun?’ You usually can’t get fingerprints from the gun. Maybe a thumbprint, but it really depends on the type of gun and the type of grip.”

Prosecutors go out of their way to explain that “CSI”-type science just doesn’t exist, Steiner said.

“It’s become so boilerplate that I could mouth the words,” he quipped. “They’ll talk about ‘blue lights,’ about how no one is coming in and putting a blue light over a bed sheet and finding semen, and then they joke, ‘You don’t want to put a blue light over a bed sheet in a motel anyway.’ ”

In cases that do use forensic evidence, meanwhile, mistakes can creep in, says Erin Murphy, a professor at NYU and author of the new book, “Inside the Cell: The Dark Side of Forensic Science.”

“Basically, if you watch these shows, they make it seem like the analyst just rolls onto the scene (usually in a skimpy T-shirt), swabs a couple objects, and then gets unimpeachable evidence of the suspect’s guilt,” she says. “But in reality, analysts must painstakingly take samples from a wide array of places and things, usually without knowing whether those efforts will pay off, and then have each tested to see whether there is any usable evidence. The testing process itself also involves a lot more subjectivity and precision than allowed in a fast-paced Hollywood drama.”

And, she adds, “Most criminal labs aren’t regulated. There’s more regulation of your local nail salon than your local criminal lab.”

DNA and forensic science “is open to the same kinds of carelessness and mishaps” as anything else.

For the defense



Of course, defense attorneys are more in favor of the influence “CSI” has had.

“More science isn’t a bad thing if it helps ensure that only those whose guilt is proven beyond a reasonable doubt be convicted,” said defense attorney Mark Bederow.

“The truth of the matter is, technology has advanced . . . someone’s life and liberty is at stake,” said Steiner. “I’ve won gun-possession cases where the prosecutor has argued that they cannot lift fingerprints off [a gun]. I’ve had jurors approach me after and say that’s why they didn’t convict my client, because of a lack of evidence.”

“CSI” science seems so unassailable, it can work for prosecutors even when it shouldn’t, high-profile defense attorney Jeffrey Lichtman argues.

He represented Paul Cortez, accused of beheading his exotic-dancer girlfriend Catherine Woods in her Upper East Side apartment in 2005.

During trial, prosecutors keyed in on a bloody fingerprint from Cortez, found on a wall in Woods’ apartment. But Cortez was frequently inside Woods’ home, Lichtman said.

“How do you know that it wasn’t a fingerprint that was already on the wall, when it was splattered with blood?” he pointed out.

The “CSI effect” has had an upside, advocates say, pointing out how DNA evidence has been used to overturn wrongful convictions, as well as pushing for more innovative investigative techniques.

“For example, one of the things that was discovered was that you could take pubic hairs from a rape kit where you didn’t have any vaginal swabs or semen, soak them in water, and literally, skin cells from the victim and the sperm from the perpetrator comes off the pubic hair and then you can analyze those,” Scheck said.

The testing led to the exoneration of a Pennsylvania man who had been in prison 30 years, he said.

“At least now when you propose something that novel, people will be responsive,” he said.

The bottom line is to get it right, veteran Bronx prosecutor Robert Dreher said.

“Either way it comes out, it’s OK with me,” he said. “I’m looking to get the right guy, I’m not looking to just get a conviction.”

For his part, “CSI” creator Zuiker is unapologetic when it comes to the impact his show has had on criminal justice.

“The ‘CSI effect’ is, in my opinion, the most amazing thing that has ever come out of the series,” he has said. “For the first time in American history, you’re not allowed to fool the jury anymore.”