Cold cases often baffle police as each year goes by with no new leads, no new evidence, and, especially, no arrest and conviction. The year 2012, however, was a good one for investigators across the country who are assigned the tough job of solving cold cases.

The following aren't the highest profile cases, but they're significant for the police departments tasked with investigating them and the families dealing with unanswered questions surrounding the loss of their loved ones.

It was DNA evidence found under the victim's fingernails and on the stockings used to tie her up that led to the December arrest of a Cleveland man in the 2006 murder of Mary Hudson.

DNA evidence led investigators to Jerome Wade after he was arrested in an unrelated felony and his DNA was put into the state system. It was later matched to Mary Hudson's murder.

Wade, 63, was arrested and indicted on December 5, 2012, by a grand jury on charges of aggravated murder, kidnapping, burglary and robbery.

Hudson's body was found lying on the bedroom floor of her East Cleveland apartment. She had been strangled and hog-tied with a stocking and a telephone cord.

In Los Angeles County, police solved a cold case murder dating back to 1980 that left a Santa Monica teenager dead. David Salmon, 53, was arrested in May at his Pittsburgh-area home in connection with the murder of 16-year-old Joaquin Mansion, who was shot by three suspects during a home invasion robbery. The residence, police said, was a known drug house.

Salmon and two juvenile suspects had demanded money and marijuana from the victim before shooting him once in the head, according to police.

The juveniles were arrested and convicted of robbery and murder. But Salmon, a transient known only by a nickname at the time, was not identified. The case went cold until it was recently reopened by Santa Monica’s cold case unit. Police have credited improvements in electronic law enforcement and databases that led them to Salmon.

In Las Vegas, ex-convict Nathaniel Burkett, who police in Nevada called a serial rapist, was arraigned and pleaded not guilty in December in the cold cases of three women killed 16 years apart. Burkett, in his 60s, appeared in a wheelchair. It was DNA evidence that linked Burkett to the cases.

He faces murder charges in the April 1978 killing of 22-year-old Barbara Ann Cox and the separate slayings of 27-year-old Tina Gayle Mitchell and 32-year-old Althea Maria Williams in 1994. Each woman, prosecutors have said, were strangled and found in a West Las Vegas neighborhood near Burkett's apartment.

And in Denver, a cold case review team this year solved four murders -- all linked to the same serial killer.

Solving the cases was the result of "extensive investigative and forensic work performed by Denver’s Cold Case Review Team,” said Lynn Kimbrough with the Denver District Attorney’s Office in a statement.

The victims -- Emma Jenefor, 25, Joyce Ramey, 23, Peggy Cuff, 20, and Pamela Montgomery, 35 -- were killed between 1979 and 1988. Evidence showed each was raped before they were murdered.

Vincent Groves, the killer, who would be 57 today, died in prison in 1996.

“They were women trying to live their lives, and their lives were taken from them by Vincent Groves,” cold case unit Detective Mylous Yearling told reporters. “Sex is about empowerment and I think that the ultimate empowerment for him was to the take the lives of other people.”

Police described Groves as "the most prolific serial murderer in the history of the state of Colorado" who "picked on weaker female victims."

But this statement from the Denver D.A.'s office perhaps best sums up what solving cold cases mean for many of the victims' families when justice is finally served:

"The closure of these four cases may provide answers to family members who have gone decades living with questions about the tragic murder of their loved one."

Recent Posts in Crime, She Writes

Robert Durst On Disappearance Of Wife: ‘I Lied’

New details revealed in HBO documentary 32 years later by person of interest

Domestic Violence: Why I Stayed and Why I Left

Grammys take a stand against violence and prompts a writer to share her story

911 Call Reveals New Details Against Former Rap Producer

Ex LAPD detective says murder case against Suge Knight may stick

A 911 New Year's Call That Foretold A Murder Is Revisited

Could a missed opportunity in the OJ Simpson murder case have made a difference?

Does The Mob Still Exist in Las Vegas? Good Question

When it comes to talk about the Mafia, 'what happens here stays here' applies

Is DNA Available From A Child Cold Case Murder 40 Years Ago?

Former neighbor of murder victim hopes crime-scene evidence leads to the killer