At the hearing, the court shall first consider only the question whether the minor is a person described by Section 300, 601, or 602. The admission and exclusion of evidence shall be pursuant to the rules of evidence established by the Evidence Code and by judicial decision. Proof beyond a reasonable doubt supported by evidence, legally admissible in the trial of criminal cases, must be adduced to support a finding that the minor is a person described by Section 602, and a preponderance of evidence, legally admissible in the trial of civil cases must be adduced to support a finding that the minor is a person described by Section 300 or 601. When it appears that the minor has
made an extrajudicial admission or confession and denies the same at the hearing, the court may continue the hearing for not to exceed seven days to enable the prosecuting attorney to subpoena witnesses to attend the hearing to prove the allegations of the petition. If the minor is not represented by counsel at the hearing, it shall be deemed that objections that could have been made to the evidence were made.