Carmen Moreno CBS News

Carmen Moreno has swept leaves and picked up garbage at Maria Luisa Park in Seville, Spain, for 28 years with little fanfare. But last week what she collected behind a park bench landed her right in the middle of her own crime scene investigation, reports CBS News' Jonathan Vigliotti.

"There was a pile of bloody tissues," Moreno said.

They were items that belonged to a 28-year-old woman who police believed overdosed on drugs and died in the park. Authorities just left the bloody items for garbage pickup, but Moreno wondered, if it was a drug overdose, why so much blood?

"This is evidence," she said -- a bold statement given her only crime scene experience came from watching her favorite American TV show, "CSI: Crime Scene Investigation."

Following what she saw on TV, she demonstrated how she used plastic bags to carefully collect the evidence without contaminating it and stored it -- just in case police ever needed it.

When an autopsy later proved the woman likely died from being violently raped, police couldn't believe they tossed vital evidence and were more stunned to learn Moreno held on to it.

The DNA evidence she collected has led to the arrest of a local suspect.

The local prosecutor credits her for closing the case. Moreno credits "CSI," saying, "You can learn a lot from the show."