Medina Spirit trainer Bob Baffert has changed his story about how the Kentucky Derby winner failed a drug test. David Begnaud reports. "CBS Evening News with Norah O'Donnell" delivers the latest news and original reporting, and goes beyond the headlines with context and depth. Catch the CBS Evening News every weekday night at 6:30 p.m. ET on the CBS Television Network and at 10 p.m. ET on CBSN. Subscribe to the “CBS Evening News" YouTube channel: http://bit.ly/1S7Dhik Watch full episodes of "CBS Evening News”: http://cbsn.ws/23XekKA Follow "CBS Evening News" on Instagram: http://bit.ly/1T8icTO Like "CBS Evening News" on Facebook: http://on.fb.me/1KxYobb Follow "CBS Evening News" on Twitter: http://bit.ly/1O3dTTe Download the CBS News app: http://cbsn.ws/1Xb1WC8 Try Paramount+ free: https://bit.ly/2OiW1kZ For video licensing inquiries, contact: This email address is being protected from spambots. You need JavaScript enabled to view it.