Jury Room Breach at Dallas County Courthouse

Tuesday, Mar 5, 2013 | Updated 9:07 PM CDT

Authorities are investigating jury room security at the Dallas County courthouses after the ex-girlfriend of a murder defendant entered a jury room and showed jurors a cellphone photo of the man's 10-year-old son.

A Dallas County sheriff's spokeswoman says testimony hadn't begun in the trial of Robert Earl Oliver at the county's criminal courts building Tuesday when the woman entered the jury room and confronted jurors in Oliver's trial.

Sheriff's spokeswoman Carmen Castro tells The Dallas Morning News the woman urged jurors to keep the child in mind as they heard the case against Oliver. State District Judge Fred Tinsley declared a mistrial and ordered a security review.

Oliver is accused of stabbing Eric Franklin to death in October 2011.