A Shefford dental manager risked inhaling dangerous mercury fumes when she drank from a poisoned cup of coffee, a court heard on Thursday (May 2).
Laura Knowles, 36, swallowed a ‘globule’ of the liquid metal before dashing away from her desk feeling sick at the Shams Moopen Dental Practice.
She suffered diarrhoea, stomach cramps and dizziness in the days that followed and suffered fits when she tried to return to work.
Trainee dental nurse Ravinder Kaur, 34, is accused of slipping the poisonous metal into the coffee in revenge for disciplinary proceedings brought against her.
Blackfriars Crown Court heard the effects could have been much worse had Ms Knowles inhaled the fumes rising from the cup.
Jurors heard expert evidence from Dr Andrew Taylor, who has studied the effects of metal poisoning for the last 40 years.
He said: “There is a good chance there was some mercury vapour around the area above the cup, depending upon how quickly it was taken and someone starting to drink it.
“Mercury would be expected to be sitting at the bottom of the cup, but stirring would cause some globules to be dispersed within the cup.
“There would be some close to the surface, which might give rise to some vapour being formed then.”
Kaur is accused of slipping the components of mercury amalgam, the metal used for fillings, into a cup of coffee shortly after 9am on March 16 last year.
Prosecutors say it was an act of ‘spiteful revenge’ after she was given a final written warning by Ms Knowles three days earlier for leaving a patient in a dental chair while she took her lunch break.
The jury has also been told tensions were raised between staff at the practice after Kaur reported a dentist at the practice to the Care Quality Commission for breaching patient confidentiality before bosses had a chance to investigate.
Dr Taylor said the potential effects of inhaling mercury include bleeding gums, breathing difficulties, and damage to the kidneys and nervous system.
He said: “Some of it will pass into the brain, and that’s where most of the effects you see are.”
“The most important thing is a change of personality, where somebody who is normally quite calm and placid, if suddenly spoken to, might burst into tears or might be suddenly aggressive and lose their temper.”
Dr Taylor said swallowing mercury is ‘not very common’, and is usually taken by people trying to harm themselves or commit suicide.
The effects are much less dramatic than if the metal is inhaled, he added.
He said: “There might be some initial effects of just drinking something which is unusual, particularly something unusual like mercury which is a heavy metal.”
“The physical presence might cause initial problems in the stomach.”
But he added he had not heard of any cases of mercury poisoning where the victim suffered symptoms similar to Ms Knowles.
Forensic scientist Dr Christopher Moynehan analysed the silver residue discovered in the sink of the dental practice and found it was the same as the contents of the mercury amalgam filling ingredients.
He said: “In my opinion, the material recovered from the sink of the staff room at the Shefford health centre is similar in chemical compound and physical appearance to the contents of the capsule.”
Ms Knowles realised immediately what had happened after she drank from the cup of coffee passed to her by Kaur and immediately began researching mercury poisoning online.
Receptionist Danielle Dickman said Ms Knowles found a ‘ring of black substance’ and had found mercury residue when she poured away the coffee.
Ms Dickman said: “All she said was she thought it might have been mercury in her cup.She looked very pale, and appeared very worried and quite frantic.’
Ms Knowles sought advice from the adjacent doctor’s surgery before taking herself to hospital, where traces of mercury were found in her stomach. Kaur was arrested that evening, and made no comment to police officers.
She later told police she believed another member of staff may have tried to frame her by putting the poison in the kettle while it boiled, in revenge for the CQC referral.
Kaur of Ettrick Drive, Bedford, denies administering a noxious substance with intent to annoy, injure or aggrieve.
The case continues.