a) It is a culturally accepted thing for people not to ‘snitch’ or become an ‘informer’
b) Although it has not happened, people fear that they would be in danger if the testified.

‘a’ is a result from an influence of foreign culture. Many dancehall songs look down upon co-operating with law enforcement, hip-hop does the same thing with the ‘don’t snitch’ movement. Young people especially tend to be greatly influenced by foreign pop culture and adopt it as their own.