From Section 7 of the Constitution of the State of Illinois:
SECTION 7. INDICTMENT AND PRELIMINARY HEARING
No person shall be held to answer for a criminal offense
unless on indictment of a grand jury, except in cases in
which the punishment is by fine or by imprisonment other than
in the penitentiary, in cases of impeachment, and in cases
arising in the militia when in actual service in time of war
or public danger. The General Assembly by law may abolish the
grand jury or further limit its use.
No person shall be held to answer for a crime punishable
by death or by imprisonment in the penitentiary unless either
the initial charge has been brought by indictment of a grand
jury or the person has been given a prompt preliminary
hearing to establish
probable cause.
(Source: Illinois Constitution.)
Definition of probable cause:
In the United States criminal court system, probable cause refers to
facts or evidence that would make a reasonable person believe that a crime or wrong doing has been, is being, or will be committed.
http://www.probablecause.org/
This information confirms that the sworn testimony of Cheif Edwards in the preliminary hearing was considerably more than his personal account or opinion of the case.