When I was a new ICU nurse we were short staffed. I finished my night shift and said 'let me get some sleep and I'll come back in and do a twilight if that helps.' So I went home, slept, then returned to do a twilight shift. It wasn't an official shift time, but I arrived at 5pm and went home at 2 am. I'm sure someone could have made something of that in a court. The fact that I was 'inserting myself into the environment', etc. In reality, I was just being kind, and slight l although I couldn't care for a patient on my own (there's a strict induction process and I was only part way through it), I could help nurses with turns, suction, drug preparation, etc.
Medicine is much more nebulous than it seems at times, especially in an emergency. In a resuscitation situation with adults, for example, you have a resuscitation leader, but everyone else is just doing their bit. You might have 4 people taking it in turns to do chest compressions, people leaning in over each other to get blood samples, administer drugs, someone on the defib, someone else on airway.... It's not chaos, but it isn a more complex situation than you see on Grey's Anatomy. There should be a scribe who records exactly who did what and when.
I haven't read extensively, but I wonder if there was an accurate log during these events at the Countess of Chester, especially as they were only holding Consultant-led ward rounds twice per week, rather than the minimum of daily that should have been. Bear in mind that some hospitals, such as University hospital Cardiff, have NICU ward rounds three times per day.
All in all, it seems like it would be very easy for someone to be accused and to have no way of proving their innocence.
As an aside, it's completely unscientific, but when I saw the documentary with her arrest in it, I thought that Lucy looked so completely stunned by her arrest that I just instinctively felt that you couldn't make up that reaction.