To prepare juice. Sort and wash fully ripe berries; remove any stems or caps. Crush berries and extract juice.
To make jelly. Measure juice into kettle. Add pectin and stir well. Place on high heat and, stirring constantly, bring quickly to a full rolling boil that cannot be stirred down. Add sugar, continue stirring, and heat again to a full rolling boil. Boil hard for 1 minute.
Remove from heat; skim off foam quickly. Pour jelly immediately into hot, sterile canning jars to 1/4-inch from top. Seal, and process 5 minutes in a boiling water bath.
This recipe yields 5 or 6 half-pint jars.