Memphis, TN - Bernard Martin's 22 year-old son, Timothy McGowan, was shot to death in South Memphis on Christmas Eve last year.

Six months later, Tim's murder is still unsolved.

"It makes me angry," says Martin.  "I don't care who's involved with it.  Everybody involved needs to go down.  I ain't gonna rest until it happens."

Martin has good reason to be frustrated.  The head of the Memphis Police Department's Investigative Services Division tells Eyewitness News Everywhere the case can't be cracked without some new information.

"It's one of those cases where we know who did it," says Major Joe Scott.  "We just can't prove it."

Scott says homicide detectives searched the area near Mitchell and Horn Lake but never found any evidence of a crime scene.   No weapon was ever recovered.  And the witness who was with McGowan that night gave cops a story that doesn't add up.

Bernard Martin's coworker, Caroline Jones, knows his pain all too well.  Her 21 year-old son, Jerome Berdin, was stabbed to death in August of 2007.

The woman who did it, Berdin's girlfriend, was never charged.   Investigators said she acted in self-defense and ruled the homicide justified.  Jones says the cops got it wrong so her family is now pursuing action in civil court.

"It's like you can commit a murder and get away with it," says Jones.  "I just don't understand."

The MPD has 18 homicide detectives pounding the pavement and cold cases are still active cases.  But without new clues or witnesses, unsolved murders remain a painful mystery for the victim's loved ones.

"Don't push him to the side," says Martin, "because I love my son.  I need to know who did it.  They need to do time for it."

So far in 2008, there have been 80 homicides in the city of Memphis.  15 of those are unsolved.   In 2007, there were 162 homicides.   23 remain unsolved.

Even though those cases are still open, the MPD's homicide solve rate is above 80-percent, which is well above the national average.  But for families waiting for justice, that statistic isn't good enough.

"Something's got to be done," says Bernard Martin.  "You have all these crimes and they're not locking people up.  What does Memphis need to do to change this? Because that's just not good enough."