The testimony came during a defense bid to rule out the conversations as evidence at the murder trial for Lane, who is accused of fatally shooting three people and wounding three others in the Ohio school's cafeteria on February 27, 2012.
The prosecution says relatives should have had no expectation of privacy while talking among themselves in a police interrogation room just after the shootings.
The trial for the now 18-year-old Lane is scheduled for January.
Investigators say he admitted shooting at students but couldn't say why. He faces up to life in prison without parole if convicted.
He has pleaded not guilty.
The News-Herald in Willoughby says Lane waved and smiled at his grandmother in court Wednesday in a rare show of emotion.