The third paragraph talks about safeguards and then tells us "however,.." indicating an issue with the safeguards/ the reason they are inadequate. Lines 25-31 tell us that there are cases when prosecutors merely imply that a cooperating witness will receive an incentive and then this conversation does not need to be disclosed to the jury, meaning that even though the cooperating witness provides testimony under the assumption that he/ she will be rewarded for it, the juries may never find out that the cooperating witness has an incentive to provide information whether truthful or not.