Dental nurse denies trying to poison boss Ms Knowles then poured the coffee down the sink where she spotted a "grey sludge" which "looked like mercury." Feeling unwell, Ms Knowles went to the hospital where an x-ray showed up white speckles above her pelvis, which the prosecution said were "speckles of metal in her intestine." Ms Knowles later confronted Kaur, who denied having put anything in the coffee. She was later arrested and a swab taken from the sink showed up a substance used to make fillings. The court heard Kaur had received training on the safe storage and handling of mercury, and was informed of the potentially fatal affects of inhaling it. In her police statement she confirmed she knew it was harmful and that she should not let it go down a patient's throat. Samantha Cohen, prosecuting, told the jury Kaur felt isolated at work after she reported another dentist to the Care Quality Commission (CQC). She complained the dentist had breached patient confidentiality, and when the dentist denied the allegations Kaur said she intended to report her to the CQC. The CQC then contacted the practice to say they had received a complaint and Ms Knowles and Kaur met on March 13 to discuss the complaint and "Ms Kaur's poor performance at work." The jury was told Kaur also refused to work with one of the dentists and on one occasion left a patient in the chair as she claimed it was time for her to have a break and eat her lunch. She had also received warnings about her performance at work. The prosecution added that Kaur, who started work as an assistant dental nurse at the practice in November 2011, believed she had been "set up" in the wake of the alleged incident. Kaur, of Ettrick Drive, Bedford, is charged with administering a poison or noxious substance when the alleged incident took place on March 16 last year.