An apparatus, comprising: evaluation circuitry (115, 125, 135) to receive program instruction execution information indicative of a program instruction executed by processing circuitry, and to perform an evaluation operation to determine the presence of a trigger condition; wherein the determination is performed by comparing the program instruction execution information with predetermined evaluation information; trigger signal generation circuitry to assert a trigger signal to the processing circuitry in dependence on whether said trigger condition is determined to be present; and filter circuitry (120, 130, 140; 365, 370, 375; 515, 520, 525) to receive event information indicative of at least one event occurring within the processing circuitry, and to determine with reference to filter control information and said event information whether a qualifying condition is present; the filter circuitry being arranged, on determining that the qualifying condition is absent, to prevent the presence of the trigger condition being notified to the trigger signal generation circuitry; wherein the at least one event indicated by the event information excludes events directly defined by execution of the program instruction; wherein the processing circuitry is arranged to execute a sequence of program instructions, said sequence including a branch behaviour setting program instruction that indicates an identified program instruction within said sequence, execution of the branch behaviour setting program instruction enabling a branch behaviour to be associated with said identified program instruction that causes the processing circuitry to branch to a target address identified by the branch behaviour setting program instruction when the identified program instruction is encountered in said sequence; and an event indicated by the event information identifies when a branch has been taken by the processing circuitry on encountering said identified program instruction due to a previous execution of the branch behaviour setting program instruction. evaluation circuitry (115, 125, 135) to receive program instruction execution information indicative of a program instruction executed by processing circuitry, and to perform an evaluation operation to determine the presence of a trigger condition; wherein the determination is performed by comparing the program instruction execution information with predetermined evaluation information; trigger signal generation circuitry to assert a trigger signal to the processing circuitry in dependence on whether said trigger condition is determined to be present; and filter circuitry (120, 130, 140; 365, 370, 375; 515, 520, 525) to receive event information indicative of at least one event occurring within the processing circuitry, and to determine with reference to filter control information and said event information whether a qualifying condition is present; the filter circuitry being arranged, on determining that the qualifying condition is absent, to prevent the presence of the trigger condition being notified to the trigger signal generation circuitry; wherein the at least one event indicated by the event information excludes events directly defined by execution of the program instruction; wherein the processing circuitry is arranged to execute a sequence of program instructions, said sequence including a branch behaviour setting program instruction that indicates an identified program instruction within said sequence, execution of the branch behaviour setting program instruction enabling a branch behaviour to be associated with said identified program instruction that causes the processing circuitry to branch to a target address identified by the branch behaviour setting program instruction when the identified program instruction is encountered in said sequence; and an event indicated by the event information identifies when a branch has been taken by the processing circuitry on encountering said identified program instruction due to a previous execution of the branch behaviour setting program instruction.