Yes, there were more deaths than average (for Chester) while Lucy Letby was on shift. I'd like to try to explain that.
Chester was a very small intensive care unit (four cots). There were always babies in the other cots, but sometimes none or only one in the intensive care cots - or sometimes up to four, with more babies needing intensive care than there were cots.
These babies were meant to have one-to-one care from a qualified nurse. This could be a level 6 nurse (more senior, better paid) or a level 5 nurse with an extra certification. There were only two of these level 5 nurses on the staff.
The unit was required to have two level 6 nurses and two level 5 nurses on every night as a minimum. One of the level 6 nurses had to be in charge of the shift. The unit had about 10-15 level 6 nurses, and about 15-20 level 5 nurses (staffing varied over the time we are looking at). And only those two level 5 nurses who were qualified to give one-to-one care.
Whenever there was more than one ICU baby on the ward, the manager needed to put either three level 6 nurses or two level 6, one level 5 with qualification, and one other level 5 on the ward that night.
Chester never in any of the shifts we have a record for (which isn't just the deaths) put three level 6 nurses on at night. It was two level 6, one level 5 with quaification, and more level 5s without. Obviously, that's the cheaper option.
So, at night you were going to try to move things around whenever you had more than one ICU baby in, to get either Lucy Letby or the other nurse with the certification. Except that the other nurse was established in her career. She had been working longer than Lucy Letby and pointed out that she rarely saw her because Lucy was the one who was willing to take on the extra shifts.
If you were a level 5 nurse without the qualification or a level 6 nurse, you could take your turn coming in at night with lots of other people. But if you were Lucy Letby, you were top of the list to come in when there were two or three or more babies needing intensive care. And of course, these were the babies most likely to die, and the more of them were on the ward, the more likely one would die.
This is why Lucy Letby's shift pattern looks different from the others. Her manager did explain this at the time. Babies, for all sorts of reasons, were more likely to die at night. And she was willing to swap around and work the night shifts with the sickest babies. When eventually she was present for two daytime deaths it was the same sort of scenario. Staffing was usually better in the day, with more level 6 nurses in, but on those days the hospital had admitted 6 - 7 babies needing one-to-one intensive care.
There are other arguments to be made around why random events can cluster, but in the case of Chester, it's also obvious from their staffing roster and the way they staffed their highest intensity shifts that Lucy Letby would very easily end up being on shift for a higher number of deaths than anyone else.
Any nurse who is in a similar position on the staffing rosters should probably make changes before their unit sees any spike in deaths, because it is a terribly vulnerable position.