"At the material time Andrew's central nervous system had been invaded by pneumococcal bacteria which in turn produced toxins. These toxins were virulent. They were countered by the body's defensive mechanisms. If the bacteria were left to produce toxins without restriction, then there was a risk that the toxins would overwhelm the body's defensive mechanisms, with fatal result. The basic purpose of chemotherapy is to inject an antibiotic into the system in order to kill bacteria without at the same time causing any, or at least any material, damage to the healthy structures of the body. If the antibiotic is injected in sufficient strength before the toxins gain the upper hand over the body's defensive mechanisms, it can tip the balance in favour of the latter by killing bacteria, and thereby preventing the multiplication of toxins. But the antibiotic does not, and is not designed to, kill toxins. No matter how effective the antibiotic may be, it remains the task of the body's defensive mechanisms to resist and to overcome the toxins. One essential component of the body's defensive mechanisms is the availability of adequate supplies of healthy oxygenated blood at and in the vicinity of the areas subjected to toxic attack.
"Applying these guidelines to the available history of Andrew's illness I consider that, on balance, Mr Williams is justified in concluding that but for the penicillin overdose, Andrew's chances of avoiding deafness would have been reasonably good."
"If the child had not received said overdose, but had received the correct dosage, his chances of recovery without any lasting deficit such as deafness would have been materially greater. The overdose in addition, and in any event, materially enhanced the risk of brain and neural damage including damage to the eighth nerve which controls hearing."
"It was submitted on behalf of the defenders that Andrew was probably deaf before the overdose was administered."
"The simple truth in this tragic case is that on the evidence (and we have examined carefully the whole evidence led at proof which the parties agreed might be relevant) the only possible conclusion was that Andrew's deafness was attributable to pneumococcal meningitis alone."
"As a medical scientist I need evidence for things, without evidence and without rational balance of evidence medicine is a dead duck and in this case there is no evidence that an overdose of intrathecal benzylpenicillin ever has caused deafness."
"All things are possible and in medicine we never say never, but from the point of view of scientific medicine to my mind there is no evidence to incriminate an overdose of intrathecal benzylpenicillin as a cause of deafness in this or in other cases and on the other side of the waterfall there is a massive amount of evidence to incriminate pneumococcal meningitis as one of the best known causes."
"To decide an issue of causation between the parties in an area of medicine where matters are very complex, and much is not yet understood, on a theory not supported by medical testimony, is neither appropriate nor just"