While often the sole source of information about an event, testimony has inherent problems as a source of information.
Due to highly constrictive regulation of refugee intakes in many western countries, especially the United State and Australia, those who claim asylum must have sufficient grounds to make a claim and for it to be sustained. Verification of events and situations, especially in areas of conflict, is notoriously difficult.
The inclination to believe often creates sympathy for refugees from what might be an otherwise cynical population. Thus, refugees may feel a moral obligation to make this sympathy 'worthwhile'.
As any enforcement or investigatory agent will explain, those who commit crimes on whatever scale seek to 'cover' their crime with a story. There is established neuroscience to support this phenomenon. Robert Sapolsky, in Behave, the best and worst of us, explains how the frontal cortex, in attempting to 'supervise' the 'reptilian' brain, will constrain behaviour to prevent an individual from 'getting into trouble' - what the religious might call 'resisting temptation'. However, in the event of discovery of the 'crime', the same area of the brain which is supposed to be 'responsible and rational' will 'flip' to attempting to construct a story which will 'justify' the individuals actions.