During the assassination of Hope Jensen.
Setup
At the start of the chase, veer left to vault over the railing instead of running into the cloud of gas unleashed by Hope. An agile guard will try to tackle you, but you'll almost always make it over the railing before that can happen.
Once outside the gate, an assassin stalker hiding on a bench will come after you, so be prepared to assassinate. From there follow the target on ground instead of taking the rooftops, where you'll always be behind her. An agile guard might still be following you, in which case sleep dart him.
Take the path in the video to reach the haystack the target uses to transition to ground level. Keep in mind Hope's immune to ranged weapons until she stops running and goes into fight mode.