One of the commonly used techniques by liberal critics of the Bible is linguistic analysis. It's used for other things and by other people too, but I'm mainly talking about that use.
One of the things they do is they look at (for example) Paul's letters, and they look at how often different words and themes occur. They they say (for example) that 1 Timothy looks very different to Romans - Philippians, so wasn't written by Paul. Noowadays, they even use computer programs for it. Or some do - most of them don't seem to know how to work computers...
There are several problems with this method of seeing who wrote what.
One is that it assumes that each author only writes in a single style - Paul might well have written differently when writing to individuals after AD60 to how he wrote when writing to churches before AD60. We know that authors do write in different styles at different times and for different reasons. Has that been factored in?
Could it analyse the novels of Iain M Banks (a science fiction author), and tell me they were all by a different person from Greg Bear (another science fiction author), but by the same person as Iain Banks (a non-science fiction author who is the same person as Iain M Banks). And what would they do with Feersum Enjinn (which is largely written phonetically and in three different styles)? I don't think it would cope; I very much doubt it has been tested.
For working within books, which is how it is often used in the Old Testament (e.g. showing that Isaiah had two or three different authors), have comparable examples been tested? Can it take a Christopher Tolkien novel and say which bits were taken from his father's notes? I doubt it. Could it take a novel by Margaret Atwood or JRR Tolkien, which tend to be written in several styles, and tell me it was the work of a single author, but the Positronic Man by Asimov & Silverberg wasn't? I doubt it.
These theories and methods annoy me. Partly because they aim to undermine stuff I believe, but largely because they're pretending to be scientific, but at the end of the day, they're just bad science.