(Editor's Note: this story contains language that may offend some readers)

CHICAGO (Reuters) - The parents of a black teenager shot and killed in December by a white Chicago police officer are accusing the policeman of a hate crime because of language used in text messages the officer exchanged before the shooting, the family's lawyer said on Friday.

The allegation is part of an amended lawsuit filed on Thursday against the police officer, Robert Rialmo, and the City of Chicago by the family of Quintonio LeGrier, 19, who was shot and killed on Dec. 26.

It said that before the shooting Rialmo would discuss whether he got "any niggas" and thought it was humorous to characterize people with that term. Basileios Foutris, a lawyer for LeGrier's parents, said by telephone that Rialmo had these discussions in text messages.

Rialmo's lawyer, Joel Brodsky, said a friend of the officer's had used the term, but Rialmo had not. Brodsky said the texts were not racist.

A 55-year-old grandmother, Bettie Jones, also African American, was killed accidentally by Rialmo during the incident.

The deaths fueled Chicago's already intense debate over police use of force against minorities amid protests in a number of cities around the United States over police killings of young black men. In the last two weeks, racially tinged violence has again shocked Americans with police shootings of black men in Louisiana and Minnesota and a black U.S. military veteran killing five white police officers in a racially motivated shooting in Dallas.

Both LeGrier's and Jones' estates sued Rialmo and the city for wrongful death.

Rialmo has counter-sued, saying LeGrier attacked him with a baseball bat, forcing him to kill him. Rialmo has also sued the City of Chicago saying he was not properly trained to reduce tensions in heated encounters with mentally ill people.

The amended wrongful death lawsuit filed on Thursday by LeGrier's family said Rialmo and the city caused a battery of LeGrier because of his race or color, constituting a hate crime under Illinois state law.

Brodsky said the hate crime allegation against his client is based on a mistaken reading of text messages.

"It's simply not any type of racist anything, it's hip-hop language that some kids use," Brodsky said.

Brodsky supplied Reuters with copies of the messages, which show that a friend texted Rialmo on Dec. 16 asking him about his work the previous night and saying "U get any niggas." Rialmo responded "Sort of lol.... long story."

(Reporting by Fiona Ortiz; editing by Grant McCool)