BRIAN ROSS REPORTS ON TRAGIC DEATH OF COLLEGE GRAD TURNED DRUG INFORMANT SENT UNDERCOVER WITHOUT TRAINING, ON "20/20," JULY 25

Plus: John Stossel's Give Me a Break -- Age Discrimination at Work; And: Do Elephants Suffer from Post Traumatic Stress Disorder? Elizabeth Vargas Reports

Are cops to blame for the controversial death of a recent Florida State University graduate who was acting as a confidential informant for the Tallahassee Police Department? After police issued a search warrant and found a "baggie" of marijuana and a couple of pills of ecstasy and valium inside 23-year-old Rachel Hoffman's apartment, Rachel told friends the officers offered her a deal of leniency instead of jail in exchange for her working an undercover drug bust. But the State Attorney's office was never told of the arrangement and Rachel never received any training from police as a drug informant before being sent alone to an undercover meeting in May with two men to buy 1,500 hits of ecstasy, cocaine and a gun with the $13,000 in cash she was carrying. She would never return from that meeting. Officers were staked-out to monitor the buy but lost contact with Rachel. Her body was found two days later. How could this have happened? Brian Ross' in-depth investigation includes exclusive, extensive interviews with Rachel's parents, friends, the police chief and the state attorney. The report airs on "20/20," FRIDAY, JULY 25 (10:00-11:00 p.m., ET) on the ABC Television Network.

And: The law says that older employees cannot be fired because of their age. When a Kansas City radio station changed music formats, they fired two DJs who had been on the air many years. The DJs are suing, charging the station with age discrimination. But John Stossel says that hiring and firing is the creative destruction that allows businesses to thrive. To the laws and lawyers that try to stop such change, Stossel says, "give me a break!"

Plus: The majority of the approximately 600 elephants living in captivity in the United States were born in the wild, separated from their families to work in our zoos or circuses. Now new science is proving that elephants have far greater emotional, social and intellectual capabilities than previously thought � and researchers argue that the trauma they experience from the separation can lead to a form of Post Traumatic Stress Disorder (PTSD). Elizabeth Vargas travels to the Mala Mala preserve in Kruger National Park in South Africa to see elephants thriving in the wild, and then to The Elephant Sanctuary, a 2,700 acre private preserve in rural Tennessee where some elephants believed to be suffering from PTSD are treated. "To diagnose an elephant with PTSD is novel, but that's because we have denied elephants the capacity of having a mind, having a psyche, having emotions. But basically the neurobiology, all the neuroscience says yes, its' there, the potential is there and the behavior confirms it," says elephant researcher Gay Bradshaw.

"20/20" is anchored by Elizabeth Vargas and John Stossel. David Sloan is executive producer.