MIAMI -- When witnesses refused to cooperate, prosecutors were forced to drop the case against reputed gang member Demarcus Alexander -- who was accused of murdering a Miami prison officer and her infant son in 2010.
Now, Alexander has beat yet another murder rap for the same reason.
Prosecutors recently dropped charges against Alexander for the unrelated robbery and murder of a Miami teenager because co-defendant Tyree Walker backtracked on a plea deal to testify against his former associate.
The lack of cooperation is yet another blow for prosecutors and Miami homicide detectives hoping to deliver justice in two high-profile murder cases. At Miami-Dade's criminal court, the fallout continues.
For Walker, his refusal to cooperate means a 17-year prison sentence will likely skyrocket when he is sentenced Oct. 19 for the murder of Garvin Webster, who was shot to death in a robbery after returning from a date at the movies in 2007.
As for Alexander, the state's fizzled cases do not mean freedom anytime soon. He's still serving a 20-year prison sentence for violating probation in an earlier armed robbery case.
Law enforcement investigators believe that Alexander was a leader in the violent Miami street gang known as "Str8 Drop," which was involved in a series of well publicized shootings in recent years.
He was one of three men initially arrested in the horrific December 2010 slaying of state corrections officer Ciara Lee, 24, and her 2-year-old son, Devin Franklin. They were killed when a group of men unleashed a volley of bullets into their Miami home -- the two were not believed to be the intended targets.
Authorities initially arrested Alexander, Tavares Williams and Henry A. Ferguson on murder and other charges. The case against Ferguson was almost immediately dropped. Only Williams -- whose DNA was found on a weapon involved in the case -- was convicted; he is serving a 22-year sentence in prison.
By April 2011, a key witness who initially told Miami police she heard Alexander discussing details of the shooting refused to continue cooperating with prosecutors. Her lack of cooperation, coupled with another key witness recanting, doomed the prosecution.
Alexander remained in jail on the probation violation.
At that point, he had long been a suspect in the January 2007 murder of Webster, who was fatally shot in front of his Allapattah home.
That night, the recent Jackson high graduate and his girlfriend, Johanna Mercado, had gone to see Stomp the Yard at the Aventura Mall. They were parked outside his home, kissing goodnight, when two young men on bicycles pulled them out of the car.
Walker, then only 16, held a gun to Mercado's head, berating her and tearing a necklace off her neck. According to prosecutors, he gave the gun to Alexander, who shot Webster in the neck.
Bloodied and gasping, Webster staggered toward his front door, knocked on the door and moments later died in his father's arms.
"'We cooperated. It wasn't like we were fighting back," Mercado told reporters afterward. "I can't even sleep. I keep replaying it over and over."
Miami homicide detectives soon arrested Walker, who lived with his grandmother. The evidence was solid -- he led police to the stolen jewelry hidden in a bedroom.
Prosecutors never had enough evidence to arrest Alexander until Walker pleaded guilty in 2012 to second-degree murder and agreed to testify. In recent months, Walker backtracked, openly refusing to testify against his one-time friend.
Defense lawyer David Pettus, during a recent sentencing hearing, admitted Walker is "fearful to testify" and asked for his client to be sentenced to 23 years in prison.
"He knows Demarcus Alexander is a killer," Pettus said. "He knows his life expectancy ... if he testified against Demarcus Alexander probably goes down to a couple of years."
Pettus stressed Walker led a troubled life. His father was murdered before his birth. His mother was addicted to crack cocaine while pregnant with him. His grandmother, a double amputee, raised him in a "chaotic" household.
"I certainly think peer pressure played a very significant factor in him getting involved with Alexander at all that day," Pettus told Miami-Dade Circuit Judge Rodolfo Ruiz.
The Miami-Dade State Attorney's Office is now asking that Walker be sentenced to at least 50 years in prison. Mercado, the surviving victim in the murder, wants the "maximum sentence," prosecutor Lisa Jacobs told the judge.
"Her life will never be the same because of what that man did to her," Jacobs said.