While short-term memory may be affected by attention and emotions, the corpus of information available to an older adult is substantial, and -- unless they show signs of progressive or absolute deterioration as in dementia -- they tend to be skeptical with a broad base of human behavior available for comparison and contrast. Psychologists suggest that the schemas of older adults tend to solidify, as people tend to look for characteristics and events that support their frame of reference. However, here again, it is important to consider the intellectual capacity and education levels of the individuals, as formal instruction requires a more disciplined, nuanced manner of thinking about the world -- which is reflected in the frames people apply to what they see and what they remember. In your opinion, what dynamic has the most adverse influence on eyewitness testimony?

The most influential dynamic on eyewitness testimony in children is the level of language development. Children -- small children, in particular -- are very attentive to details that would be considered close up in their environment. That this is so is evident in the keen ability and propensity for imitating adult behavior and speech. However, as events move further away from a child's central sphere of attention, relevancy diminishes and,...

If there is a particular attraction to an event or situation that is a bit out of child's immediate, typical realm -- such as the presence of a parent, sibling, animal, music, and the like -- then the child's attention will be diverted. A novel situation can also compel a child's attention. But the fact remains, that even if a child's attention is focused on an event, the words to label, process, and perhaps later describe the event are typically not yet assimilated by a young child. Moreover, if a child is fearful -- for specific or even nebulous reasons -- word-finding capacity may be limited even more.
Huitt, W., & Hummel, J. (2003). Piaget's theory of cognitive development. Educational Psychology Interactive. Valdosta, GA: Valdosta State University. Retrieved http://www.edpsycinteractive.org/topics/cognition/piaget.html

Kulfosfky, S. And Kemfuss, J.Z. (2008). What the stories children tell can tell about their memory: narrative skill and young children's suggestibility. Developmental Psychology, 44(5), 1442-1456.

Wilde Astington, J. And Edward, M.J. (2010, August) the development of theory of mind in early childhood. Encyclopedia on Early Childhood Development. [Web.] Retreived http://www.child-encyclopedia.com/documents/Astington-EdwardANGxp.pdf