The Hittite treaties changed shape over time. Archeology has uncovered several examples of sometimes radical differences from one century to the next. The 10 Commandments are shaped like a Suzerainty Covenant, so is the book of Deuteronomy. When these forms are laid out next to the 10 Commandments or Dt, they both conform to the treaties from 1,200-1,500 BC.
This find challenges the documentary hypothesis because the odds of randomly putting the correct form together several centuries later (when other forms are in use) is low. It could be argued that a sage would have an example of an older form. But to think that the sage would say, "Hey, in 2,800 years, archeologists are going to know about these older forms, so to make this look like Moses wrote it, I'd better use that instead of the current one. What year are we conspiring to say Moses lived in again?" has low probability. Likewise, editing together works from multiple authors would be difficult to do while keeping the shape.
Order of sections in Hittite Treaties, mid-second millenium BC
The treaties varied over time and a newly uncovered treaty can be quickly dated based on the order (and presence) of certain sections.
Section Exod Dt Josh 24
Intro of speaker 20:1 1:1-5 1-2a
Historical Prologue 20:2 1:6-3:29 2b-13
Stipulations 20:3-17 cc 4-26 14-15, 23
Renewal 25:16 27:2-3 25-26a
Witnesses none. cc 31-32 22, 26b-27
Curses ch 28 19-20
Oath of Allegiance 24:3 16-18, 21, 24
More information can be found here and at Bible.org.
In 800 BC, when the documents were supposed to be written according to the documentary hypothesis, the sections had been rearranged. Section 2 is missing (and the whole of Hebrew concept of nation relies on the historical prologue), and often blessings and curses are gone. Most importantly, there is no evidence from any Hittite or related culture that the older form was known after the fall of the United Monarchy (Mendenhall, "Covenant Forms in Israelite Tradition" in Biblical Archeologist 17:3 (May 1954):50-76.) Let's be careful because an absence of evidence is not evidence of absence, but it is something to think about. No less than W. F. Albright points out that the structure of all the treaties known from six neighboring civilizations in the 8th century and later are all quite different.