Prince Watson, 17, is charged with murder in the death of Sally Katona-King on March 28. Prosecutors said Watson pushed Katona-King down the stairs at the CTA's Fullerton stop while he fled a robbery.
Katona-King, 68, suffered multiple ribs, a fractured skull and bleeding in her brain. She died the next day.
Watson is accused of stealing an iPhone from a passenger on a Brown Line train at the elevated platform. Police allege he sold the iPhone for $350 to 400.
Prosecutors said Watson made a videotaped admission.
"The defendant stated that after he bumped into those ladies, he heard screaming but never turned around because he didn't want anyone to see his face," Toni Giancola said.
"I certainly haven't seen any videotaped confession. And I certainly know that . . . videotaped confessions of a 17-year-old don't necessarily always hold up in court or are worth anything," Michael Mayfield, a Cook County public defender, said.
Detectives said Wednesday that Watson was identified through surveillance video and witness statement. The suspect was already behind bars, serving a four-year sentence in a separate case in which he stole another iPhone.
In that incident in May, Corrie Besse, 31, followed Watson after he grabbed her iPhone at the Clark and Division stop. She flagged down police and Watson was arrested nearby.
"When somebody rips something from your hand, your immediate reaction is to chase after them, for me. I don't know about other people," Besse said.
Investigators say that incident, which occurred two months after Katona-King's death, helped them connect the dots.
"It's just a real tragedy what happened to that woman, and I'm just really thankful and hopefully I provided some closure for the family," Besse said.
Watson has also been charged with a third iPhone theft incident in April at the Sedgwick Brown Line stop.
Prosecutors say witnesses at all three incidents have positively identified Watson. But Watson's attorney questions if those accounts are credible.
"This was an incident that was very quick and the eyewitnesses testified like four or five months later, and definitely the credibility of those have to be tested," Mayfield said.
Watson's criminal history includes a 2007 aggravated battery and 2008 robbery. In court, Judge Adam Bourgeois Jr. called the suspect a "dangerous individual." He is being held without bail.
In response to these and other iPhone thefts on CTA trains, Guardian Angels began longer patrols on trains Thursday afternoon.