CAN A PERSON BE BOTH A
CHRISTIAN AND A WICCAN?
Overview of "the problem"
It is quite possible for a person to follow a syncretistic religion -- a faith involving elements from two or more religions. This is sometimes disparagingly called "shopping-cart religion." However, it is a common practice, particularly in the Far East. Many New Agers blend certain Christian and New Age beliefs and practices. So, a person could both:
 Worship the Christian God, believing in the resurrection of Jesus, virgin birth, second coming and other historical Christian teachings.
 Believe in selected elements from Wicca, such as  respecting nature, caring about the environment, celebrating at solstices, equinoxes, harvest festivals, etc. 
However, they might not necessarily be viewed as a fellow Christian or a fellow Wiccan by more conventional followers of these two religions.
Main difficulty -- beliefs in deity:
Merging the conflicting beliefs about deity found in two religions is often the main problem area in creating a syncretistic religion:
 Most contemporary Christians regard themselves as monotheists, and believe in the Trinity, composed of the Father God, the Son Jesus, and the Holy Spirit. These are three different persons within the same Godhead. "Wisdom" is described in various places in the Bible as a type of female Goddess who was present at the creation of the universe. However, she does not play a significant role in most modern Christian faith groups. 
 Wiccans believe in a duo theistic deity structure: a Goddess and a God. Further, the Goddess has three aspects: Maiden, Mother and Crone. They represent sexuality, fertility and wisdom. 
At first glance, the beliefs of Wicca and Christianity concerning deity appear to be hopelessly at variance with each other. But some Wiccans have been able to integrate Christian and Wiccan elements into a single spiritual path.
Why conservative Christians may reject a Christian/Wiccan religious blend:
Most Conservative Christians reject the concept that a Wiccan can be a Christian. 1 Some of the problem areas are:
Many define a Christian quite narrowly. They include only those who have repented of their sins, has trusted Jesus as their Lord and Savior, and has accepted certain core traditional Christian teachings. (e.g. the Trinity, Incarnation, resurrection of Jesus, virgin birth, heaven, hell, sin, salvation, original sin, the existence of Satan as a living entity, etc.) Many of these are incompatible with Wiccan theology.
 Many conservative Christian denominations teach that women should not be in a position of power over a man, either in church, at work, or at home. Such a belief is totally at variance with Wiccan beliefs who generally believe in sexual equality. 
 Religious conservatives generally teach that homosexuality is unnatural, abnormal, chosen, changeable and intrinsically sinful. Most Wiccans disagree with these beliefs, accepting the findings of human sexuality researchers that a homosexual orientation is normal and natural for a minority of adults. Further, an orientation not chosen and cannot be changed. 
 Many conservative Christians believe that various forms of divination are an integral part of Wicca. Since the Bible contains passages condemning many of the divination techniques which were in use in ancient times, they assume that there is no room for Wiccan belief within Christianity. They overlook that some forms of divination were condoned by the Bible. One was even used by temple priests. Also, while it is true that some Wiccans engage in divination, not all do.
 Wiccans would have to abandon many traditional biblical teachings in order to consider themselves to be Christian. However, millions of Americans already reject major portions of the Bible, and still consider themselves as Christians. For example, most liberal Christians probably reject certain themes and stories in the Bible as not representing the Will of God. These might include: genocide, human slavery, burning some hookers alive, whipping children with a rod, raping female prisoners of war, execution of non-virgin brides, executing people who work on the Sabbath, executing sexually active persons with a homosexual orientation,  executing religious minorities, etc. 
It is clear that a Wiccan cannot consider themselves to be Christian without first rejecting much of the content of the Bible and many historical Christian beliefs. This would exclude them from the conservative Christian fold in the same way that liberal Christians are considered to be non-Christian or sub-Christian by many religious conservatives.
Why liberal Christians may accept a Christian/Wiccan syncretistic religion:
Among liberal Christians, the term Christian has generally been defined much more broadly. For example, some believers might accept as a Christian any person who holds Jesus in reverence, views him as the greatest of prophets, and tries to follow his teachings. Many Wiccans, Humanists, Unitarian Universalists can match this definition.
Resolving the deity question
Many Wiccans (perhaps most) believe that there is a single ultimate deity which/who is unknowable. A common Wiccan saying is that "All Gods are the ONE GOD." This deity is sometimes referred to as "The All" or "The One" and is often visualized as having two aspects: a male facet who is called the God and a female component, the Goddess. Christianity also teaches the existence of a single God. 2 But most denominations teach that God has a different internal structure. The Chrisitian God does not have two aspects. Their God is a Trinity, composed of the Father, Son and Holy Spirit.
About the male aspect of deity: There were about 50 gospels and dozens of letters and essays written by the early Christian church. However, only four gospels and various letters that were accepted into the Christian Scriptures (New Testament). Those four tell of a unified Christian movement which regarded Yeshua of Nazareth (Jesus Christ) to be the Son of God and a deity. Other documents -- which never made it into the official canon -- describe a divided Christian movement. They explain that, after Jesus was executed by the Roman Army, (circa 30 CE) and a few  years before Paul returned to organize his churches (circa 35 CE), Jesus' disciples organized a reformed Jewish movement that is normally referred to today as the Jewish Christians. They regarded Jehovah, as described in the Hebrew Scriptures (Old Testament), to be a single, indivisible God. They regarded Jesus as a human, and a great prophet-king. Details are lacking, but they may well have regarded Wisdom as a type of female supernatural presence who was with God at the creation of the world - a type of Goddess. A Wiccan might consider these non-canonical gospels and writings to be accurate and adopt beliefs similar to those of the early Jewish Christian movement. Wiccans might associate Jesus with the male aspect of "The One."
 About the female aspect of deity: Some Wiccans and liberal Christians believe that Jesus married Mary Magdalene. The marriage ritual at Cana described in the Gospel of John may have referred to their marriage. They honor Mary as the Goddess of Christianity -- as representing the female aspect of "The One." Others substitute or include: Miriam, the mother of Jesus;
 Sophia, the Goddess of wisdom who is described in a number of places in the Hebrew Scriptures as a separate, female personality; 
 Mother Earth; and/or 
 Asherath, a Goddess worshiped by many ancient Hebrews. 
3 Considering Jesus as a wise teacher:
Throughout the past 2 millennia, there have been many beliefs among Christians about the nature of Jesus of Nazareth. He has been considered by various Christian and secular groups as:
A religious King, 
 A God, 
 A Lord,
 An itinerant rabbi in Palestine during the first century CE,
 A native healer,
 A gifted prophet, 
 A spirit being who only appeared to be a human, and 
 various combinations of the above. 
This diversity of thought continues today:
 Some liberal Christians believe that Jesus was the greatest of all of the Prophets, but not the Son of God, and not a component of the Trinity. 
 Muslims believe that he was a great Prophet and teacher. 
 Most modern conservative and mainline Christians believe that he was God, one of three components of the Trinity (along with God and the Holy Spirit). 
Many Wiccans view Jesus as a great teacher and prophet. So, one could be a Wiccan, believe that Jesus was a great teacher, and be in accordance with many believers in the early Jewish Christian movement, and with some liberal Christians today. Their deity could then be "The One" with a male and female aspect.
Resolving the 10 commandments problem:
Some of the 10 commandments do present a problem:
Thou shalt have no other gods before me." Interestingly enough, this passage seems to indicate that the author of the 10 commandments acknowledges the existence of other gods beside Jehovah. However, the commandment does seem to prohibit worshiping the Wiccan god and goddess, whose personalities are very different from Jehovah's.
Concerning graven images: Many Wiccans do use statues on their altars; these would violate the commandment. However, others use candles, feathers, etc. to represent the god and goddess symbolically ; these should present no difficulty. 
Concerning taking the Lord's name in vain: This should not present a problem.
Remember the Sabbath (Friday sundown to Saturday sundown) and keep it holy: This conflicts with the Wiccan worship schedule which includes 8 Sabbats, 13 or so full moons and perhaps 13 new moons per year - a total of about 34 Sabbats and Esbats -- less than the approximately 52 Sabbaths of Judeo-Christianity. The former are based on the phases of the moon and on the sun, not on a seven-day week. However, most Christians have deviated from the Ten Commandments by observing Sunday as the Sabbath. Perhaps a further change would be acceptable. 
Concerning the honoring of parents: Many Wiccans would have difficulty expecting children to honor very abusive parents, but then so would liberal Christians.
Concerning murder: The prohibition matches the Wiccan Rede.
Concerning adultery: This also matches the Wiccan Rede.
Concerning stealing: Most Wiccans probably believe that stealing is acceptable in certain unusual circumstances - in life-threatening circumstances, for example. But then, liberal Christians would as well.
Concerning perjury: Again, this matches the Wiccan Rede.
Coveting the neighbor's possessions: In the original Hebrew, the word that is translated as "covet" contains the meaning of desiring inordinately -- a real craving. Many Wiccans would probably agree that obsessing over a neighbor's possessions is undesirable. However, Wiccans in general would reject the concept that a male neighbor's possessions include his wife and slaves.
Wiccans would certainly have difficulty following all 10 commandments and harmonizing them with their own theological and moral beliefs. However,  Christians have similar problems: most don't worship on Saturday; many have statues of the Virgin Mary and crucifixes. Yet they still consider themselves to be Christian.
Handling important teachings of Jesus:
Hell: Jesus is described as believing in a Hell where evil people will be tortured with fire, heat, and worms for all eternity. They will live in "darkness: there shall be weeping and gnashing of teeth." (Matthew 25:30). The adjacent passage (Matthew 25:31-46) describes how those destined for heaven will be separated from those who will be sent to Hell on the basis of their works while on earth -- specifically their kindness to the poverty stricken, sick, disabled, imprisoned, and hurting. Essentially all Wiccans would assert that the existence of Hell is incompatible with their concept of a loving and forgiving Goddess and God. Liberal Christians generally regard the material about Hell in the Christian Scriptures (New Testament) to be symbolic in nature. The passages are seen to reflect the growing theology of the early Christian movement and may not represent the original teachings of Jesus. Other Christian denominations teach different views. A Wiccan can thus reject the Bible's concept of  Hell and still agree with some Christian faith groups.
Role of women: Generally speaking, the Hebrew Scriptures severely restricted the status and roles of women. Jesus preached a revolutionary message about gender equality. St. Paul continued these teachings, and put them into practice with the selection of many female co-workers. Subsequent authors, writing in the name of Paul, gradually reverted to teaching a subservient role for women. Many of the more liberal Christian denominations reject the Hebrew Scriptures' view of the status of women, and ignore the later Epistles in the Christian Scriptures. These are seen primarily as expressions of Jewish and Pagan culture. Liberals give much greater weight to the teachings of Jesus. Most Wiccans hold very strong beliefs in gender equality. They would feel more comfortable with the teachings of liberal Christian faith groups.
Biblical teachings about Witchcraft
Most conservative Christians believe that the Bible contains many specific condemnations of Witchcraft, and that these denunciations apply to Wicca as well. (e.g. Exodus 22:18 - "Thou shalt not allow a Witch to live.") Liberal theologians point out that the word in the Hebrew Scriptures that is commonly translated as Witch or Witchcraft really refers to the practice of reciting curses which are intended to hurt or kill other people. The Greek word in the Christian Scriptures that is translated Witch is unrelated to Wicca. It would be better translated as "one who concocts potions to kill people," or simply "poisoner." Such activity by Wiccans is, of course, prohibited by the Wiccan Rede which does not allow believers to harm, manipulate, control or dominate other people. It may be safely concluded that references to Witch and Witchcraft in the Bible do not relate to Wicca.
Biblical teachings about divination
There are many verses in the Bible that prohibit certain methods for foretelling the future by the ancient Israelites. These include Exodus 22:18, Leviticus 19:26-26; 19:31; 20:6; Deuteronomy 18:10-11; Isaiah 8:19 and Malachai 3:5. Of these, Deuteronomy 18 is perhaps the most important. They forbade the Israelites from engaging in eight specific practices. Various translations of the Bible use various ambiguous terms or phrases here: augur, black magic, calls up the dead, charmer, consults with spirits, divination, enchanter, fortune teller, interpret omens, look for omens, magician, medium, necromancer, observer of times, sorcerer, soothsayer, spiritist, weaves or casts spells, witchcraft, and wizard. The terms magician, sorcerer, spiritist, and witch have many different meanings.
Clearly, translators have had a great deal of difficulty selecting unique English words or short phrases to match the Hebrew text. Returning to the original words:
yid'oni Making contact with spirits (not of God). This would probably forbid the New Age practice of channeling.
sho'el 'ov Making contact with the dead. This would probably prohibit a medium from contacting the dead, as in Spiritualism.
qosem q'samim Foretelling the future by using lots. This would condemn casting runes, using the I Ching or a similar system
m'onen Predicting the future by interpreting signs in nature. (e.g. predicting the harshness of a winter by looking at moss on trees, or fur thickness on animals in the wild, or whether the groundhog sees his shadow)
m'nachesh Enchanting (perhaps related to nachash, a snake; i.e. snake charming)
chover chavar Casting evil spells by magical knot tying
m'khaseph evil sorcery; using spoken spells to harm other people
doresh 'el hametim Literally "One who asks the dead", probably via another method than sho'el 'ov
Divination techniques are used by many, but not all, Wiccans. They typically utilize only a few: #3 prohibits runes, perhaps tarot cards, the I Ching. #4 prohibits prediction of the future by interpreting natural signs. The Biblical passages appear to apply to persons who are directly engaged in the various practices (e.g. mediums, channelers, astrologers, etc.); they do not seem to refer to people who simply observe the activity.
However, there are a number of instances in the Bible where respected leaders were involved in divining the future, apparently without any condemnations by God. Some are:
In Genesis 44:5, Joseph's household manager refers to a silver drinking cup "...in which my lord drinketh and whereby indeed he devineth". Later, Joseph accuses his brothers of stealing the cup, saying "that such a man as I can certainly divine [the identity of the thieves]". These passages show that Joseph engaged in scrying to foretell the future.
 The Urim and Thummim were two objects mentioned in Numbers 27:21 and 1 Samuel 28:6 of the Hebrew Scriptures. They were apparently devices (perhaps in the form of flat stones) that the high priest consulted to determine the will of God. They might have worked something like a pair of dice.
 The prophet Daniel was employed for many years in Babylon as the chief occultist to the king. He was supervisor "of the magicians, astrologers, Chaldeans and soothsayers". See Daniel 5:11.
In conclusion, Wiccans could avoid the relatively few divination techniques that are forbidden. They could use those methods that Joseph, the priests and Daniel used. They could also use techniques that are not specifically prohibited. Or they might not directly use any method of foretelling the future and merely observe others.