IMO, sexual abuse is much worse than physical abuse. If some of the stories that I've read are true, TH was guilty of both with his children and physical with his wife. I'm not sure that I believe all of the stories about JMB as some of those people, IMO, were simply seeking their 15 minutes. As to TH, most of the stories are from Pam's relatives and could also be biased.
So, discounting the supposed abusive nature of both men, what is left? First and foremost is the mtDNA evidence that indicates that in all likelihood either TH or David Jacoby (or both or people who share maternal ancestors with them) was (were) at the discovery site. TH has said, over and over, that he was in and out of that 2.5 acre patch "all night long" searching for Stevie. Jacoby has stated that he did not search the discovery area. So, the most likely explanation for the hairs is that TH is responsible for them.
Additionally, TH has holes in his alibi. JMB does not. For instance, David Jacoby stated in his deposition for the Pasdar suit that TH was playing guitars at his (Jacoby's) house on the evening of May 5, 1993, from about 5:15 pm or 5:30 pm until about 6:15 pm or 6:30 pm. Then, TH left to look for Stevie. He returned later (other testimony puts the return at about 7:30 pm or 7:45 pm) at which time David joins in the search while Amanda is left with David's wife, Bobbye. Then, again, TH goes off alone. In short, there are several stretches of time during which TH was alone. All of JMB's time has been documented as having been spent with at least one other person.
Now, if you are truly wondering about Mark's apparently conflicting statements, I can summarize his explanation in the book (pp. 70 - 76). However, if you are simply wanting to cast doubt on Mark, I doubt that the explanation will satisfy you. However, here is a summary from the book.
Mark said that when he said that the knife had not been used he was referring to hunting. He misunderstood Gitchell's question to be in reference to hunting and not a general question regarding whether or not the knife had ever been used. So, his statement was simply an affirmation that the knife had not been used for hunting. He also mentioned that, due to the medication he was on (I am assuming the anti-depressant), he did have trouble remembering everything clearly.
A great deal of attention was paid to the fact that the blood on the knife matched Chris' type. However, little mention was made of the fact that Mark and Chris share the same blood type. Remember, there are only four basic blood types in human beings: A, B, AB and O. When the Rh factor is consider, the types are doubled to eight. The types are not equally distributed, however. So, the fact that Chris and Mark share the same blood type although they are not biologically related is really not all that remarkable.
The whole incident of the Kershaw knife was really a red herring. The defense, as is their job, was trying to establish reasonable doubt of their clients' guilt. Mark just happened to provide a possible avenue.
As a further example of what I'm saying, consider the necklace video:
[ame="http://www.youtube.com/watch?v=NKnGYZfuBBQ"]Deleted scene from Paradise Lost - Necklace - YouTube[/ame]
Although the blood on the necklace had the same type as both Jason and Stevie, the prosecution had no intention of pointing out that the blood could have been Jason's (who often wore the necklace and could have easily cut himself shaving while wearing it and left the "specks" on it). All they wanted to establish was that the blood matched Stevie's type. The necklace was never discussed from the stand because it didn't really provide any inculpatory evidence. OTOH, the defense introduced the Kershaw knife because, although not exculpatory, it could have provided reasonable doubt for their clients.