A grand jury decided on Thursday not to charge a Texas police officer who was shown on a cellphone video throwing a black teenage girl to the ground outside a pool party last year, the authorities said.

The footage of the white officer, Cpl. David Eric Casebolt, tackling the teenager in June 2015 was posted to YouTube, becoming part of a nationwide debate over how white officers treat African-Americans.

Tom Mills, a lawyer for Mr. Casebolt, who resigned from the McKinney Police Department in the wake of the encounter, said on Friday that the officer was “very relieved” by the grand jury’s decision.