John the Baptist may have been a member of the Essene sect of Judaism. Several of the disciples of Jesus may also have been members. Jesus himself may have been an Essene prior to receiving his mission, as in the Book of Mark.
As for the legal state of John the Baptist, again staying with Mark's version, he was beheaded prior to Jesus receiving his mission, there was no christianity to convert to until after the crucifixion, leaving John a full fledged member of the Essene sect of Judaism. Even if John did accept Jesus as the Messiah he died without being aware that Jesus would die. Had he lived longer than Jesus and not refuted Him legal woes occur.
John is a controversial character in the New Testament. In the Gospel of Luke before visiting Joseph and Mary to announce the miraculous virginal birth Mary will have, an Angel visits John the Baptist's father to announce the upcoming birth of John. John's Mother is Mary's sister. John the Baptist and Jesus are cousins, according to the Gospel of Luke.
In the Book of Acts the Apostle Paul is forced to abandon his planned missionary route in order to hurry to a church he established previously because the membership there is falling into the worship of.............John the Baptist. What the heck? Paul's second mission occurred around 20 years after the crucifixion of Jesus.
Back to the Essenes, they were a very liberal sect of Judaism greatly influenced by the Persian faith, Zoroastranism. They returned to Jerusalem 200 years after their ancestors had been taken captive in the Babylonian Exile, paving the way for Christianity. The Essenes believed in an afterlife, resurrection of the dead, heaven and hell and an adversarial relationship between Satan and God, all foreign to Orthodox Judaism and the religion of Moses. They also believed God was surrounded by an endless number of Angels. There was an even more radical cult of the Essenes, a monastic cult which stayed away from civilization, taking up residence in caves where they studied the Old Testament Prophets and eagerly awaited the coming of "The Teacher of Righteousness" and were intensely interested in literature concerning Angels. These monks were the people of the Dead Sea Scrolls.