A 500-year-old mummy that was discovered more than 10 years ago was found to have a lung infection and the method used to find the sickness could improve the accuracy of forensic science in criminal cases.

The mummy called "Maiden" is a 15-year-old Incan girl who was sacrificed 500 years ago along with two other Incans in some sort of ritual, scientists claimed. The findings were recently published in the journal PLoS One.

Instead of using DNA samples, which can be unreliable at times, researchers used protein samples of the specimen, which are able to better withstand environmental conditions. Along with this, they used a new method called shotgun proteomics, which analyzes the amino-acid sequences in proteins.

"Being the expression of DNA, proteins really show you what the body is producing at the time when the individual is being sampled- or, in our case, at the time of death," Angelique Corthals, study researcher and forensic anthropologist at the City University of New York, told LiveScience.com.

For the study, researchers took lip swabs from two of the Andean Inca mummies. One was from a 7-year-old boy and the other was from Maiden.

"What I really wanted to do originally was see where the blood I found on the mummies' clothing and lips came from," Corthals said. "But we found a whole lot more than we were expecting."

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The mummies were first discovered during an expedition in 1999 and were found buried in snow and ice on the summit of the Argentinian volcano Llullaillaco, which is 22,100 feet above sea level.

The pair is believed to have been part of an ancient ceremonial ritual in which the two were both sacrificed. After the pair was buried, freezing temperatures and other natural factors keep the two preserved over the centuries.

But researchers explained that new techniques used on these mummies could one day be used to improve the reliability of forensic science.

"I expect [the method's] biggest impact will be in criminal forensic science," Corthals said.