BOLIVAR, Mo. -

Bolivar's new police chief is taking another look at the past.  Chief Mark Webb has been on the job four months.  By listening to the public and looking through old files, he's found several cases he believes need a closer look.  One of those is the death of David Sims, 27.

It's been more than three years since Christina Allen lost her son.

"David has the most contagious personality.  At his funeral, people would walk up to me and say, 'David was my best friend,' because he made everybody feel like that; you were his best friend," Allen said.

On Sept. 18, 2010, a woman took Sims, unconscious, to an emergency room.  She said she found him in the Esquire theater parking lot.  That story doesn't sit right with Webb. 

"Okay, something's not right here.  So the nurses begin asking questions, and the people that brought him just kind of vanish," Webb said.

Sims lived 10 days in a coma.  As he was being taken off life support, Allen saw her son's smile one last time. 

"I know now, the smile was, he was looking into the face of God," Allen said.

Allen says her son struggled with addiction to painkillers after two surgeries following a car accident.  She thought rehab had worked, but doctors found Fentanyl in his system.

"If somebody's providing an illegal controlled substance that somebody lost their life on it, obviously we want to try to seek any kind of criminal charges we can," said Webb.

Allen says Bolivar police spoke with her once in the beginning, then nothing. 

"There were so many unanswered questions, and it was so hard to sit and think that the Bolivar Police Department, in 2010, looked at my son's life as not even worth investigating his death, that he was just a write-off," Allen said.

Former police chief Steve Hamilton re-opened the case earlier this year, and Webb is now taking the lead. 

"To ensure that people got justice is the bottom line.  That's the ultimate goal," Webb said.

Allen is hopeful that closure will finally come. 

"I feel like, by the time he's done, I'm going to know what happened to my son, I'm going to close that door, and I'm going to move on from there," Allen said.

Webb says he's looked at about a dozen other cases, and cleared up some clerical errors and things that had fallen through the cracks.  

There are four other cases of deceased persons that Webb says he's examining further.  They include the death in 2012 of a 54-year-old man that was ruled a suicide, the death in 2009 of a 6-week-old baby, the death in 2009 of a 53-year-old man whose body was found near his garage, and the death in 2006 of a 24-year-old woman that was ruled a suicide.