Police say they have to rely more on scientific evidence and less on the testimony of witnesses because a popular television show has changed the expectations of jurors and crime victims.

The "CSI effect" is named after the highly rated crime drama that, in three different incarnations, follows teams of crime scene investigators.

Like any good prime-time drama, the action on CSI is fast-paced, and the mysteries are all solved within an hour. The characters are shown using high-tech gadgets and scientific reasoning to catch criminals and build air-tight cases.

Staff Sgt. Tony McCulloch of the RCMP's forensics unit.

The effect will be a topic of discussion this week as 200 forensic specialists from across Atlantic Canada gather in Halifax.

Staff Sgt. Tony McCulloch of the RCMP's forensics unit in Halifax says people are developing unrealistic expectations of the type of evidence needed to build a case.

"When we go to crime scenes, we have a much more significant interest from victims of the crime who want to peer over our shoulders and offer their opinions, and actually kind of play into the investigation because of their intrigue with it," said McCulloch.

Some jurors are now becoming more interested in forensic evidence and less trusting of witness accounts, McCulloch said. He said this leads to problems for officers working on cases, such as a theft or a break-and-enter, where certain types of evidence aren't normally taken.

"We're going to have to present our evidence to the courts and ultimately to the jurors, and they're going to have a certain potential expectation of the forensic evidence that was recovered from the scene," he said.

If there's no DNA or fingerprint evidence, investigators are finding they have to explain why there isn't, McCulloch said.

Steve Smith, a researcher at Saint Mary's University who has been studying the CSI effect, said people need to understand that it's not practical or feasible for police to do a full investigation in every situation.

"For example, it may not be worth a police officer's time to do extensive fingerprinting and DNA analysis for something as simple as a break-and-enter," Smith said.

Smith will be speaking at this week's training seminar about the impact of television shows on how investigators do their work.