I have gathered, selected, and edited many of the quotations from my own comments on the previous post in this series…

The Fourth Gospel plays an important role in determining the probability of the claim that Jesus died on the cross. Two of the key injuries allegedly inflicted upon Jesus are documented only in the Fourth Gospel:

1. Jesus’ hands and feet were nailed to the cross.
2. Jesus was stabbed in the chest with a spear while on the cross.
Marcus Borg, a leading Jesus scholar and member of the Jesus Seminar:
“Cumulatively, these differences have persuaded scholars that a foundational choice must be made: The historical Jesus was either more like the Jesus of the synoptics or more like the Jesus of John. The differences are so great that the synoptic and Johannine portraits of Jesus cannot be harmonized into a single whole. For mainline scholars, the choice is the synoptics.”
(Jesus at 2000, p.132)

But it is not just the liberal scholars of the Jesus Seminar that doubt the historical reliability of the Fourth gospel and the traditional view that John the apostle wrote the Fourth gospel. Several Evangelical NT scholars and conservative Jesus scholars and moderate Jesus scholars doubt or reject the view that the apostle John wrote the Fourth gospel, and doubts about the historical reliability of the Fourth gospel are also common among NT and Jesus scholars who are moderate or conservative scholars.

One 20th Century scholar who has been a leading proponent of the view that the Fourth gospel should be treated as a legitimate historical source is D. Moody Smith: “In his book of the same title, Maurice Casey asks, is John’s Gospel true? and answers that is not. Given Casey’s standard of what is truth (cf. John 18:38), his answer is in many important aspects correct, or so I would agree. The picture of Jesus as the Christ that emerges from John is significantly farther removed from the historical Jesus than that portrayal of any or all of the Synoptic Gospels. It is true, as Casey maintains, that John is influenced both by the synagogue conflict, which so largely shaped the Gospel in its formative stages, and by its post-resurrection, Christian perspective…. John’s Jesus is different from the synoptic Jesus, and both differ from the historical figure of Jesus. Yet John’s Jesus is a more distinctly Christian figure who stands over against ‘the Jews.’Casey’s argument that the Gospel of John is untrue entails his maintaining that in all cases where it differs from or contradicts the Synoptics John is historically wrong. Doubtless he believes that is the case, but his arguments suffer from his palpable programmatic intention. If, in respect to major and central aspects of John’s portrayal of Jesus, Casey’s position is, by historical-critical standards, largely correct, this does not mean that the Fourth Gospel may not contain historically accurate data, particularly when its differences do not express its clear theological or narrative interests.”
(John Among the Gospels, 2nd ed., p.234-235)

Evangelical NT scholar Rodney Whitacre:
“I will refer to John as the author not in the sense that he necessarily wrote it all as it stands, but in recognition that it is his witness that is presented here and that he at least caused it to be written (21:24).”
(John, IVP New Testament Commentary, p. 21)

Evangelical NT scholar George Beasley-Murray:
“The Beloved Disciple is not a member of the Twelve, nor a well-known person in the early Church. […] The Beloved Disciple is not the author of the Gospel-neither of chaps. 1-20 nor of chap. 21. […]He [the Beloved Disciple] is the prime source of the traditions about Jesus in the Johannine circle. […] As with the Beloved Disciple, so with the Evangelist [the author of the Gospel]: we do not know his name.”
(John, Word Biblical Commentary, Vol. 36, p. lxxiii-lxxiv)

Evangelical NT scholar M.M. Thompson:
“A common understanding of the Beloved Disciple is that he is a person who heard and followed Jesus, although he was not one of the Twelve. … He exercised a role of leadership in one group of early Christian congregations, probably gathering a circle of disciples around him. One (or more) of his disciples wrote the Gospel, but who this author is remains unknown to us.”
(IVP Dictionary of Jesus and the Gospels, p.370).

Evangelical NT scholar I. Howard Marshall:
“These facts lead most scholars to conclude that John could not have been the author of this Gospel. However, the weight of the evidence for some connection between John and the Gospel is so strong that many scholars feel unable to deny that John had something to do with the Gospel. …. On the whole, therefore, it is improbable (although not impossible) that John himself wrote the Gospel, but very probable that his influence lay behind it.”
(I Believe in the Historical Jesus, revised edition, p.150-151)

Ben Witherington III, one of the top Evangelical NT scholars:
“There are a variety of good reasons to think that this author is not John son of Zebedee, not the least of which is that the Fourth Gospel leaves out all the special Zebedee stories we find in the synoptics involving events that John was a special eyewitness of (for example, the raising of Jairus’s daughter, the transfiguration, and the request for special seats in the kingdom). Yet there is a strong stress in the Fourth Gospel on the author being an eyewitness of other events in the life of Jesus. The most reasonable conclusions are the following: (1) John of Patmos wrote Revelation but not the gospel or epistles of John; (2) the Fourth Gospel and the Johannine epistles were not written by John son of Zebedee either; (3) rather, those documents were penned by the Beloved Disciple, who is someone else–a Judean disciple of Jesus, as we shall see.”
(What Have They Done with Jesus?, p.142)

James Dunn, a leading conservative Jesus scholar:
“…few scholars would regard John as a source for information regarding Jesus’ life and ministry in any degree comparable to the Synoptics.”
(Christianity in the Making, Volume 1: Jesus Remembered, p.165-166)
“…John’s Gospel cannot be regarded as a source for the life and teaching of Jesus of the same order as the Synoptics.”
(Christianity in the Making, Volume 1: Jesus Remembered, p.166)

N.T. Wright, another leading conservative Jesus scholar:
“John (I shall refer to him by that name without prejudice as to which of the possible ‘Johns’, if any, he actually was; likewise, without reaching any conclusion either on the identity of the beloved disciple or on his relation to the actual author of the book [the Fourth Gospel]) …”
(The Resurrection of the Son of God, p.662)

Graham Stanton, a conservative Jesus scholar:
“Today it is generally agreed that neither Matthew nor John was written by an apostle. And Mark and Luke may not have been associates of the apostles.”
(The Gospels and Jesus, p.135)

Richard Burridge, a conservative Jesus scholar:
“The identity of this mysterious ‘Beloved Disciple’ is greatly debated. … If the gospel went through

several versions over a long period of time, the apostle John may have been the original story-teller, whose preaching brought this church into being, but from the text, we simply cannot know.”
(Four Gospels, One Jesus? p.157-158)

Conservative Jesus scholar Bruce Chilton:
“John’s Gospel, for example, is routinely dismissed as a source, on the grounds of its obviously homiletic purpose, comparatively late date, and greater distance from the culture of Galilee and Judea. … But the complex development of that Gospel over time has been amply demonstrated by Raymond Brown in his commentary. Its earliest sources, he argues convincingly, are comparable to the Synoptic tradition in value, although independent…. Given the way in which much early Christian and Judaic literature developed within communities in phases, rather than by the work of single authors who took responsibility for everything they wrote, it is unrealistic to simply write such texts off completely as fiction. It is clear that when materials in John and other sources can be shown to be early on literary grounds, and to accord with and complement what we may deduce from the Synoptic Gospels, it should be used with caution.”
(Rabbi Jesus, p. 301)

Craig Evans is a conservative Jesus scholar, and an Evangelical Christian scholar. In his book Fabricating Jesus, there are hints that Evans does not accept the traditional views of the authorship of the Gospels: “At first, I must admit, I found aspects of biblical criticism unsettling. But in time I realized that what biblical criticism challenged was not the essence of the Christian message, but the baggage that many think is part of the message. Typically this baggage includes views of authorship and dates of given biblical books (for example, the idea that biblical books must be early and written by apostles even when they make no such claim), as well as assumptions regarding the nature of biblical literature (for example, the belief that the Gospels are history and nothing else)…”
(Fabricating Jesus, p.13)

Craig Evans apparently also views the Fourth gospel as a somewhat unreliable source of the words of Jesus, as do most other Jesus scholars. See a theology student’s comments on a dialogue between Craig Evans and Bart Ehrman on the question ‘Can We Trust the Bible on the Historical Jesus?’:http://thecenterfortheologicalstudies.blogspot.com/2011/03/gospel-of-john-and-problem-of.html

Craig Evans and Robert Gundry (an Evangelical NT scholar) both recommend an introductory textbook on the historical Jesus by a conservative scholar Michael McClymond; the book is called: Familiar Stranger: An Introduction to Jesus of Nazareth. (Eerdmans, 2004).

McClymond, as with most NT and Jesus scholars, does NOT ‘put the Gospel of John on a par with Matthew, Mark, and Luke’ as an historical source for the life of Jesus. He states as a ‘foundational principle’ for the study of the historical Jesus that: “… the Gospel of John is quite different from the other three Gospels, and it is primarily in the latter that we must seek
information about Jesus.”
(Familiar Stranger, p.35)

According to the moderate-to-conservative NT scholar C.K. Barrett it is a ‘moral certainty’ that the Fourth gospel was NOT written by John the son of Zebedee: “It must be allowed to be not impossible that John the apostle wrote the gospel; this is why I use the term ‘moral certainty’. The apostle may have lived to a very great age; he may have seen fit to draw on other sources in addition to his own memory; he may have learnt to write Greek correctly; he may have learnt not only the language but the thought-forms of his new environment ( in Ephesus, Antioch, or Alexandria); he may have pondered the words of Jesus so long that they took shape in a new idiom; he may have become such an obscure figure that for some time orthodox Christians took little or no notice of his work. These are all possible, but the balance of probability is against their having all actually happened.”
(The Gospel According to ST. John, 2nd ed., footnote on p.132)

C.K. Barrett summarizes his view of the historical unreliability of the Fourth gospel: “It is evident that it was not John’s intention to write a work of scientific history. Such works were extremely scarce in antiquity, and we have seen that John’s interests were theological rather than chronological. Moreover, his treatment of the only source (Mark) we can isolate with any confidence from his gospel is very free; and there is no reason to think that he followed other sources more closely. He did not hesitate to repress, revise, rewrite, or rearrange. On the other hand there is no sufficient evidence for the view that John freely created narrative material for allegorical purposes. His narratives are for the most part simple, and the details generally remain unallegorized. This means that the chronicler can sometimes (though less frequently than is often thought) pick out from John simple and sound historical material; […] It was of supreme importance to him [the author of the Fourth gospel] that there was a Jesus of Nazareth who lived and died in Palestine, even though to give an accurate outline of the outstanding events in the career of this person was no part of his purpose. He sought to draw out, using in part the form and style of narrative…, the true meaning of the life and death of one whom he believed to be the Son of God, a being from beyond history. It is for this interpretation of the focal point of all history, not for accurate historical data, that we must look in John.”
(The Gospel According to ST. John, 2nd ed., p.141-142)

There is an article on the Fourth Gospel in The Oxford Companion to the Bible. That article was written by a moderate-to-conservative NT scholar, Stephen Smalley. In the article, Smalley does not challenge the traditional view that the ‘beloved disciple’ was John the apostle. However, Smalley has concluded that there is a history of various stages of development behind the Fourth Gospel that puts some significant distance between John and the final written product that we now call the Gospel of John.