Section 624. Evidence

Only competent, material and relevant evidence may be
  admitted  in a fact-finding hearing; only material and relevant evidence
  may be admitted in a dispositional hearing. Evidence of parental contact
  or of failure to maintain contact with a child subsequent to the date of
  the filing of a petition under this part shall be  inadmissible  in  the
  fact-finding hearing. Such evidence may be admitted in the dispositional
  hearing  but  shall  not, of itself, be sufficient as a matter of law to
  preclude or require an order committing the guardianship and custody  of
  the child.