John 3:18

Is not judged

(ου κρινετα). Present passive indicative. Trust in Christ prevents condemnation, for he takes our place and pays the penalty for sin for all who put their case in his hands (Romans 8:32). The believer in Christ as Saviour does not come into judgment (John 5:24).Hath been judged already

(ηδη κεκριτα). Perfect passive indicative of κρινω. Judgment has already been passed on the one who refuses to believe in Christ as the Saviour sent by the Father, the man who is not willing to come to Christ for life (John 5:40).Because he hath not believed

(οτ μη πεπιστευκεν). Perfect active indicative of πιστευω, has taken a permanent attitude of refusal. Here οτ μη states the reason subjectively as the judgment of the Judge in any such case (ο μη πιστευων already mentioned) while in 1 John 5:10 οτ ου πεπιστευκεν gives the reason objectively (ου instead of μη) conceived as an actual case and no longer hypothetical. See John 1:12 for εις το ονομα with πιστευω (believing on the name) and John 1:14 for μονογενους (only begotten) and also John 3:16.