It's clear this is not one of these academic books that people forget having read instantly. To illustrate the impact of sources, Thurén uses real life examples like the disappearance of the heroic Raoul Wallenberg during the second world war, the murder of the Swedish prime minister in the 80's, Olof Palme, and other murders. This brings a authentic perspective to the book that also serves as confirmation of the importance the author applies to sources.
It's difficult to decide whether sources are affected by other people, the environment or the conventions of society and whether the questions asked are open or closed, leading the sources to truthful or false statements. Another thing to consider is how much time that has passed since the actual event. A person's memory tends to be more reliable just after something happens than years later, but at the same time the memory might be blocked because of chock. At the other hand, even though the memory gets worse in the beginning, the deterioration slows down after some time and it doesn't matter if the person is interviewed one year or five years later. Furthermore, people remember what they are interested in, whatever time has passed. These facts really emphasize the complicated world of journalism.
The book does digress sometimes, but it's important issues that needs reflexion.