In a lawsuit the first to speak seems right, until someone comes forward and cross-examines.
NMV[He that is] first in his own cause [seems] just; but his neighbour cometh and searches him.
OJBHe that is harishon (the first) to make his case seemeth tzaddik, but his re'a cometh and doth cross-examine him.
T4TThe first person to present his case in court seems right, but when ◄someone else/his opponent► begins to ask him questions, it may become clear that what he said was not true.