A judge appreciates a retracted confession with great caution: first he must see whether it was voluntary and true, and if satisfied, he should still ordinarily look for independent corroboration in material particulars before acting on it.
30-second answer
“A retracted confession is not to be rejected merely because it is retracted, but the court must examine it with great caution. The first test is whether the confession was voluntary and truthful, free from threat, inducement, or promise. If the court is satisfied on these points, the confession can legally be acted upon; however, as a rule of prudence, the judge should seek independent corroboration in material particulars before basing conviction on it.”
One-line version
“A retracted confession is admissible, but the judge must first test its voluntariness and truth, and then ordinarily seek material corroboration before relying on it.”