In each of these speech acts, an understanding of linguistics can play an important role in investigations and trials. Solicitation is, as the authors write, "asking or inducing someone else" to commit a crime, usually a serious crime. So prosecutors must prove, beyond a reasonable doubt, that a solicitor "intended the crime to be committed." Whether or not the crime is actually carried out is irrelevant to the guilt or innocence of the solicitor. But regardless, it has to be proven that the accused was not joking, or exaggerating, or trying to make some point.
As the authors write, semantics is crucial to cases of solicitation. In order to prove this crime, they write, it must be proven that the "speech act" is clearly "a request ... offer or command." Intent is crucial: precisely what one says (the "illocutionary act") is less important than the goal of the speech (known as the "perlocutionary act").
In other words, the key question is this: What does a person hope to gain by saying what they said? In the cases they cite in the chapter, the accused have gone beyond suggesting a crime to make specific requests—promising, or at least pointing out, that the solicited individual will receive some benefit (or, in the case of a command, avoid a negative consequence) by carrying out the proposition. The larger point is that linguistics is crucial to this process: "The essence of solicitation," the authors write, "is language."