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DELPHI, Ind. – Six months into the search for the killer of Abby Williams and Libby German, we are learning new information about the evidence police are using to track down the suspect.

“It takes a lot of time and we want to be very thorough and make sure that all i’s dotted and t’s crossed. This is a tough case,” said ISP First Sgt. Jerry Holeman.

It is a case the ISP Lafayette District Investigative Commander has worked every day for the past six months.

“We are getting closer every day. I know that is cliché but we are,” said Sgt. Holeman.

Dozens of state, local and federal agencies are still working around the clock to track down the man they believe killed Abby and Libby while the girls were out on a walk on the Delphi Historic Trails in February.

“We are stronger than ever and we are getting more people involved, so I think that the time is coming,” said Sgt. Holeman.

Police tell us they have conducted hundreds of interviews, followed up on thousands of leads and served dozens of search warrants to find clues that the killer may have left behind, including DNA.

“At every crime scene, you are going to have DNA. We are still working on identifying all of the DNA that we have there,” said Sgt. Holeman.

Along with DNA evidence, police also have the suspect’s voice. Police tell us Libby recorded the killer’s voice on her cell phone, telling the girls to go down the hill. Investigators say she hit record after he approached them near the Monon High Bridge.

Sgt. Holeman tells us investigators have more audio from Libby’s phone, which was found with the girls at the crime scene.

“It does not appear to be anything more than some discussion between the girls. We have only released a portion of it. There are some others we think could help us but again protecting the integrity of the investigation is key so we cannot release everything because there are certain people that know the details and if we release it all then we get into false confessions,” said Sgt. Holeman.

Sgt. Holeman tells us several people have come forward and said they saw the killer walking on the trails the day Abby and Libby were killed. Those people helped develop a composite sketch that was released last month.

“We have to go off of the evidence that we have: the composite drawing, the video, and the audio,” said Sgt. Holeman.

As officials work to process the evidence, ISP has a group of detectives interviewing and re-interviewing people in connection to the case. This process is to ensure investigators did not miss anything along the way.

“Is there anything that we did or did not do to jeopardize the case? No,” said Sgt. Holeman.

The main focus for investigators is to get the killer off of the streets, bring closure to Abby and Libby’s families, and justice to the girls.

“I still believe that someone knows what happened and won’t come forward and we wish that they would because this person is probably going to do this again,” said Sgt. Holeman.

If you have information on the case call 844-459-5786, your tip can remain anonymous.

Watch the interview with Sgt. Holeman here: