DENVER (AP) – Denver’s top two law-enforcement officials disagree on the answer to what ought to be a simple question: Is violent crime up or down?

Police Chief Robert White and District Attorney Mitch Morrissey aren’t quibbling over minor details; they have a 17 percentage point difference in opinion about the way crime is trending. Experts say their disagreement underscores the complexities of measuring and interpreting crime trends in a major city.

White has repeatedly said violent crime fell more than 8 percent last year. Morrissey wonders how that can be true when felony cases submitted to his office rose 9 percent during the same time.

“One of the things you can glean from it is that the crime rate is going up. It has to be. (The police) are presenting more cases to us,” Morrissey told The Denver Post. “The trend is that our caseloads are getting bigger and bigger. How is that possible with the crime rate going down? I don’t know.”

White stood by the 8.6 percent decline he has boasted about at public gatherings and in police stations, saying it was the result of better policework, even with fewer officers on the street.

“How about the fact that maybe the police department is doing a better job of arresting the right people?” White said. “His cases are going up because the police are out there working their butts off and doing a better job. That’s not rocket science.”

But there is some science to crime statistics, said Callie Rennison, an associate professor in the University of Colorado Denver’s School of Public Affairs.

“It’s a hard, hard thing to measure, which of course makes it hard to say, ‘Well is it really going up or really going down?’” she said. “Anyone who tells you, ‘Here’s my stat, it’s a perfect one,’ immediately don’t trust them. No stat is perfect, but some are less perfect than others.”

White said his figures are based on numbers the department presented to the FBI for its annual Uniform Crime Report. He said they are a more accurate reflection of crime in the city than another set of data posted on the department’s website that indicates a 13.9 percent increase in crimes against people last year.

Those are the police department’s crime data classified under the National Incident Based Reporting System, which measures the individual crimes contained within a single incident. If, for example, someone is killed during a robbery, the NIBRS numbers include both a homicide and a robbery. The Uniform Crime Report that White points to includes only the most serious crime, so the same incident would be classified only as a homicide.

Rennison said NIBRS is a better gauge of crime because it offers a broader view of different types of offenses.

Driving the 13.9 percent increase in the NIBRS numbers was a 71.5 percent increase in intimidation offenses and a 28.8 percent spike in simple assault, neither of which are offenses included in the Uniform Crime Report, said Chris Wyckoff, director of the police department’s data analysis unit.

Crimes such as those seemed higher last year because of a change in the way police officers report them, she said. Certain citations would be reported directly to court under the old system, so they would not have been captured in the statistics.

Of the Uniform Crime report and NIBRS, Wyckoff said, “The numbers change constantly because they are dynamic. I would expect, in time, some of these numbers will go up, but in some cases they will do down because we’ve found that some of them didn’t even occur.”

White said the Uniform Crime Report is the national standard for crime reporting and what big city departments compare themselves against. But doubts were raised last year about the accuracy of the figures that Denver police were submitting to the FBI after officials acknowledged that hundreds of crimes were not included because of officer error and computer glitches. Twenty-five percent of 2012’s homicides, for example, were not reflected in that year’s preliminary Uniform Crime Report.

White said he is confident that the problem is “98 percent fixed” and this year’s Uniform Crime Report is accurate.