If you're talking about more than one justice, the correct plural is justices. The singular possessive is "justice's"; the plural possessive is "justices'."
The plural of justice is justices.
The plural of Justice of the Peace is Justices of the Peace.
The plural form of chief justice is chief justices.
Lord justices.
Justices.
Singular possessive: secretary's Plural: secretaries Plural possessive: secretaries'
The plural is lads. The plural possessive is lads'.
The plural is relatives. The plural possessive is relatives'.
The plural form is suffixes. The plural possessive is suffixes'.
The plural form is stepsisters. The plural possessive is stepsisters'.
The plural form is Mexicans. The plural possessive is Mexicans'.
The plural form is echoes. The plural possessive is echoes'.