The mother of 1 of the drowning victims at Carl Crawford's Texas mansion last month says the former MLB star is responsible for her son's death ... and now, she's suing for over $1 million.
It's all spelled out in new court docs obtained by TMZ Sports ... in which Liban Hersi claims 38-year-old Crawford didn't do enough to prevent tragedy from striking on May 16.
In the docs, Hersi says her 5-year-old son was visiting Crawford with a family friend for a party at the former L.A. Dodgers outfielder's mansion in Harris County, Texas.