An Indian-origin nurse is on trial in the UK over charges that she attempted to "poison" her boss by spiking her coffee with mercury amalgam used in dental fillings.
Ravinder Kaur, 34, denies administering a poisonous or noxious substance with intent on March 16, 2012, three days after being given a warning about "poor behaviour" at work.
A jury at her ongoing trial at Blackfriars Crown Court in London was told that her boss, Laura Knowles, went to hospital and lost consciousness after returning to work following the alleged incident.
The 36-year-old said she also had bouts of dizziness, diarrhoea and vomiting.
Prosecutor Samantha Cohen told the court that Kaur had begun work as an assistant dental nurse at Shams Moopen Dental Practice in Shefford, Bedfordshire, in November 2011.
She started out as "meticulous and professional" but her behaviour soon changed with colleagues regarding her as inflexible and "not a good team player".
In January last year, she had received a verbal warning for unfairly ordering her colleagues around at work.
On March 13, the nurse was summoned to a meeting to discuss her "generally poor behaviour" by Laura Knowles.
A few days later, she offered to make coffee for Knowles, but did not return for 15 minutes.
The court was told that her boss noticed the drink did not taste right and when pouring away the coffee spotted a grey sludge in the sink.
She then started to feel sick and suffer stomach cramps.
The prosecution said X-rays showed the presence of "speckles of metal" in Knowles' lower intestine consistent with "ingested mercury".
Kaur was arrested later that day and prosecutors said swabs of sludge found in the sink matched the mercury amalgam used by the surgery to make fillings.
They told the jury that Kaur was trained in the use of mercury and was taught how to handle it safely and deal with spillages.
The defendant claims she had been set up by members of staff because of her reports to the authorities.