WILL A DISTRAUGHT TEEN'S TEXT BE THE KEY EVIDENCE NEEDED FOR A JURY TO CONVICT A STRAIGHT-A STUDENT OF HOMICIDE?

Was This a Suicide Attempt or a Terrible Accident Involving Driving and Texting?

Plus: A Life and Death Rescue Caught on the High Seas

Was it an accident or a suicide attempt at 80 mph on a highway that shattered one life and killed two other innocent people? Justine Winter was a 16-year-old straight-A student with a bright future. But one night, while breaking up with her boyfriend, she texted him that she wanted to end her life. Just a few minutes later, her car collided with a car carrying Erin Thompson and Erin's 13-year-old son, Caden. Both were killed instantly, yet somehow Justine survived and was charged as an adult with two counts of homicide. But was it? Did she deliberately kill a mother and her son, or did something else happen that night? Deborah Roberts reports on the tragedy, the trial and the aftermath, on "20/20," FRIDAY, AUGUST 19 (10:00-11:00 p.m. ET on the ABC Television Network.

Plus: A life and death rescue on the high seas caught on tape... One tiny boat and a 30-foot whale, trapped in a fishing net in a race against time.

"20/20" is anchored by Elizabeth Vargas and Chris Cuomo. David Sloan is executive producer.