In any situation, everyone involved will have a different memory of what happen. This is especially true whenever there's a crime. "He fell down the stairs." "She pushed him." "He backed into the knife… twelve times." That type of thing.
Now imagine how varied the memories would be when the crime happened twenty years ago. In the Woods deals with two different cases—a present-day crime, and a two-decades-old cold case in which the primary witness was a preteen. We can't even remember what we did the summer we were twelve, and no one tried to murder us in the woods, so while we think we'd remember that, we're actually not so sure.
Questions About Memories and the Past
Why has Rob repressed his memories?
What strategies does Rob use to try to recover his repressed memories? Are they effective? Should he have left these memories repressed?
When Rob starts recovering memories, what does he remember? Which memories does he end up keeping and which memories does he try to forget again?
How do different characters (such as Rob and his mother) remember things differently?
Chew on This
The longer it takes for a crime to be solved, the harder it is to solve it, because all the witnesses' memories become more like legends than truth as the years go by.
It's possible Rob is pretending not to remember—he is a liar, after all—to hide his involvement in the 1984 crime.