A magistrate judge.
Another View: Define specifically what you are referring to by the use of the phrase, "administer justice."
Also: Are you referring to US District Court or to a State District Court.
In the US District Court system there are both Magistrate's and Judges.
More specifics about what is being asked must be known before an answer can be given.
The person who administers justice in a district court is the district court judge
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magistrate
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court
The Chief Justice of the Supreme Court.
chief justicethe Chief Justice of the Supreme Court
The Chief Justice of the Supreme Court.
Chief Justice of High Court
The chief justice of the supreme court administers the oath in normal times.
Chief Justice of the Supreme Court
Chief Justice of the Supreme Court