Someone who is implicated in something is shown to be somehow involved in it. The word is often used in a negative sense, suggesting an involvement in something wrong, with the person being implicated by the facts of the case.
The Latin word implicātus, which means "folded in," is the past participle of implicāre, meaning to interweave ideas or objects. In the 17th century, the word referred to a general entanglement in a complicated situation. By 1797, the definition had come to focus on the idea of criminal involvement, suggesting someone "folded in," or involved, in a crime or scandal. Today, the word implicated is not necessarily tied to crime, but it's generally negative.