A raised metal slide which allowed a tiger access to a paddock where it killed a zookeeper would have been easily visible to a person performing checks, an inquest heard.
Rosa King, 33, was savaged by a Malayan male called Cicip while she worked alone cleaning the paddock at Hamerton Zoo Park in Cambridgeshire.
She died at the scene on May 29 2017.
Sergeant James Thorne, of Cambridgeshire Police, told an inquest in Huntingdon that tigers could only access different areas within their enclosure when permitted to do so by zoo staff.
Tigers and keepers were never meant to be in the same section, with keepers supposed to locate the tiger and isolate it in a different section before entering the paddock.
Steel slides, which were raised and lowered on wires connected to a series of pulleys, controlled where the tigers could go.
The slides were padlocked into position, either raised or lowered, at a position near the keepers’ entrance where the counterweights were.
Mr Thorne said he found no mechanical faults and that it was easy to spot the position of slides.
“There are no obstructions to the view,” he said, adding: “For me it was quite apparent as you walk into that enclosure which slides were open and which ones were closed.”
Elizabeth Yeomans, a senior ergonomist for the Health and Safety Executive, conducted what she called a “human failure analysis” of the zoo’s procedures.
She said a keeper could “forget to check” where the tiger was before entering the paddock or “could have a memory lapse or be distracted by something”.
“You could just assume that the tigers are in the den as they always are in the morning,” she said.
“It’s these kind of errors that you could make.”
The inquest previously heard that Ms King was on duty the evening before and may have left a tiger in the paddock overnight.
Ms Yeomans said the zoo did not require keepers to record the tiger’s location and it was a visual check only.
She assessed it as “unlikely” that a keeper could make a mistake about whether a tiger was there if they had looked.
She said a keeper could forget to check that the slides were closed, or be distracted or assume that they were closed “because they usually are”.
She said it was “possible” Ms King made a slip, completing checks but getting her actions wrong, “but I don’t think it’s very likely because of her level of experience”.
She added she did not think Ms King deliberately skipped a step in the procedure as the “evidence is she was a very responsible and meticulous person”.
Asked by Cambridgeshire assistant coroner Nicholas Moss about the type of circumstances where human error can occur, Ms Yeomans said: “Things like pressure to achieve, something you’re rushing, you’re tired.”
The inquest previously heard Ms King had been helping with night feeds for a serval kitten, a type of African cat, but colleagues described her as being her normal self on the morning she was attacked.
Ms Yeomans said that sometimes, when a person has completed a task many times before, “you look and see what you think you should see”.