What is the test for liability in a motor vehicle accident?

to anyone 'concerned, ' however slight such concern may be, for the law establishes no degree of the concern required to fix liability as a principal." [Citation.]' [Citation.] 'It has been held, therefore, that one who is present for the purpose of diverting suspicion, or to serve as a lookout, or to give warning of anyone seeking to interfere, or to take charge of an automobile and to keep the engine running, or to drive the "getaway" car and to give direct aid to others in making their escape from the scene of the crime, is a principal in the crime committed. [Citations.]' [Citation.]" (People v. Swanson-Birabent (2003) 114 Cal.App.4th 733, 743-744.)