See bibliography under Pharisees.
Rabbinic tradition suggests that they were not named after the High Priest Zadok, but rather another Zadok (who may still have been a priest), who rebelled against the teachings of Antigonus of Soko, a government official of Judea in the 3rd century BC and a predecessor of the Rabbinic tradition.
The Dead Sea Scrolls community, who are probably Essenes, were led by a high priestly leadership, who are thought to be the descendents of the "legitimate" high priestly lineage, which the Hasmoneans ousted. The Dead Sea Scrolls bitterly opposed the current high priests of the Temple. Since Hasmoneans constituted a different priestly line, it was in their political interest to emphasize their family's priestly pedigree that descended from their ancestor, the high priest Zadok, who had the authority to anoint the kingship of Solomon, son of David.
Most of what is known about the Sadducees comes from Josephus, who wrote that they were a quarrelsome group whose followers were wealthy and powerful, and that he considered them boorish in social interactions (see Josephus's Wars of the Jews, Book II, Chapter VIII, Paragraph 14). We know something of them from discussions in the Talmud (mainly the Jerusalem), the core work of rabbinic Judaism, which is based on the teachings of Pharisaic Judaism.
And a man, when he maims his fellow, as he has done, so shall be done to him. A fracture for a fracture, an eye for an eye, a tooth for a tooth—as he gives a wound in a man, so shall be given in him. (Leviticus 24:19-20)
Most Pharisees understood this to mean that the value of an eye was to be sought by the perpetrator rather than actually removing his eye too. In the Sadducees' view the law was to be taken literally.
R' Yitchak Isaac Halevi suggests that while there is evidence of a Sadducee sect from the times of Ezra, it emerged as major force only after the Hasmonean rebellion. The reason for this was not, in fact, a matter of religion. He claims that as complete rejection of Judaism would not have been tolerated under the Hasmonean rule, the Hellenists joined the Sadducees maintaining that they were rejecting not Judaism but Rabbinic law. Thus, the Sadducees were for the most part a political party and not a religious sect (Dorot Ha'Rishonim). Professor Lawrence Schiffman also cites interpretations of the purity regulations in the Dead Sea scroll "MMT" (ca. 150 bce) which closely parallel Sadducean views recorded by the spiritual heirs of the Pharisees, who authored the Talmud (Oral Law). But more importantly, he identifies very detailed Pharisaic (or proto-Pharisaic) views in the MMT scroll. Thus, it can no longer be argued that there is no pre-Temple evidence for the Oral Law. However there is evidence that there was an internal schism among those called "Sadducees" - some who rejected Angels, the Soul, and Resurrection - and some which accepted these teachings and the entirety of the Hebrew Bible.
In regard to criminal jurisdiction they were so rigorous that the day on which their code was abolished by the Pharisaic Sanhedrin under Simeon ben Shetah's leadership, during the reign of Salome Alexandra, was celebrated as a festival. The Sadducees are said to have insisted on the literal execution of the law of retaliation: "Eye for eye, tooth for tooth", which pharisaic Judaism, and later rabbinic Judaism, rejected. On the other hand, they would not inflict the death penalty on false witnesses in a case where capital punishment had been wrongfully carried out, unless the accused had been executed solely in consequence of the testimony of such witnesses.
According to the Talmud, they granted the daughter the same right of inheritance as the son in case the son was dead (see chapter Yeish Nochalin of the Babylonain Talmud, tractate Bava Batra). Emet L' Yaakov explains that the focus of their argument was theological. The question was whether there is an afterlife (see above), and if there is, can the dead person be in the line of inheritance as if they were alive.
According to the Talmud, they contended that the seven weeks from the first barley-sheaf-offering ("omer") to Shavuot (Pentecost in Christian reference) should, according to Leviticus 23:15-16, be counted from "the day after Sabbath," and, consequently, that Shavuot should always be celebrated on the first day of the week (Meg. Ta'an. i.; Men. 65a). In this they followed a literal reading of the Bible which regards the festival of the firstlings as having no direct connection with Passover, while the Pharisees, connecting the festival of the Exodus with the festival of the giving of the Law, interpreted the "morrow after the Sabbath" to signify the second day of Passover.
In regard to rituals at the Temple in Jerusalem:
None of the writings we have about Sadducees present their own side of these controversies, and it is possible that positions attributed to "Sadducees" in later literature such as Josephus are meant as rhetorical foils for whatever opinion the author wishes to present, and do not in fact represent the teachings of the sect. Yet, although these texts were written long after these periods, many scholars have said that they are a fairly reliable account of history during the Second Temple era.
Josephus relates nothing concerning the origin of the Sadducees; he knows only that the three "sects" — the Pharisees, Essenes, and Sadducees — dated back to "very ancient times" (Ant. xviii. 1, § 2), which point to a time prior to John Hyrcanus (ib. xiii. 8, § 6) or the Maccabean war (ib. xiii. 5, § 9).
Among the rabbis of the second century the following legend circulated: Antigonus of Soko, successor of Simeon the Just, the last of the Men of the Great Assembly, and consequently living at the time of the influx of Hellenistic ideas (i.e., Hellenization), taught the maxim, "Be not like servants who serve their master for the sake of a reward, but be rather like those who serve without thought of receiving a reward" (Avot 1:3); whereupon two of his disciples, Zadok and Boethus, mistaking the high ethical purport of the maxim, arrived at the conclusion that there was no future retribution, saying, "What servant would work all day without obtaining his due reward in the evening?" Instantly they broke away from the Law and lived in great luxury, using many silver and gold vessels at their banquets; and they established schools which declared the enjoyment of this life to be the goal of man, at the same time pitying the Pharisees for their bitter privation in this world with no hope of another world to compensate them. These two schools were called, after their founders, Sadducees and Boethusians.
The Acts of the Apostles likewise indicates that Sadducees did not share the Pharisees’ belief in a resurrection; Paul starts a conflict during his trial, by claiming that his accusers were motivated by his advocacy of the doctrine of the resurrection (in an aside, Acts 23:8 asserts that “The Sadducees say that there is no resurrection, or angel, or spirit; but the Pharisees acknowledge all three”).