Regarding the second statement in the title, modern medical evidence would probably make it easy to show that the defendant was or still is suffering from the disease (as opposed to another sexual partner which the victim may have had). Recklessness as to its transmission would depend on the facts of each individual case but for the most part it is fairly clear: if the defendant had sex with the victim with the knowledge that he had the infectious disease then that is sufficient for the purposes of recklessness.
It would not need to be in his mind at the time (which could be the case due to the dominant nature of sexual excitement and enthusiasm) as long as he was aware that he carried the disease. Matters can get more complicated, however, when the defendant does not know whether or not he carries a sexually transmissible disease or where the victim has had more than one sexual partner who carries the infection. The latter situation is, thankfully, quite rare and will not be considered further in this essay.
As the title statement correctly ventures, 'it will be harder to prove recklessness where the carriers do not know that they are infected'. Of great importance here are the individual facts of the case, as it could come down to a matter of degree. A defendant who was a medical student exhibiting all the symptoms of a sexual disease, and suspected an infection, but did not go to a doctor to get it confirmed could be said to have been very reckless in having unprotected sex with a partner who did not know about the symptoms or the student's suspicion.
However, if someone who knew very little about medicine had a near-symptomless sexual disease and over whom the thought of being infected had only crossed his mind once or twice, then had sex and transmitted a disease without telling his partner of his very temporary concern, then it would be much more difficult to maintain that he had been reckless. What if this same person was normally a hypochondriac and assumed that he was being paranoid about the diminutive symptoms he did notice on occasion?
The medical student and the hypochondriac are two extremes, and there will be many hard cases inbetween when a jury will have to make a decision based on the facts. There are many other considerations to be taken into account if this is to be criminalised. Policy reasons – do we want to force people to disclose personal information about themselves to sexual partners? One could argue that a sexual partner denotes an intimate relationship and such information should be disclosed. On the other hand it could be argued that it is one's right to keep personal information to oneself.
Many will feel deeply sensitive about any possible disease and not wish to share such concerns. It could be feasible to make people visit their doctor before proceeding with sexual intercourse. Along the same lines is the moral argument of whether or not people ought to inform others and whether they ought to visit a doctor. However, what if the test results were incorrect? Could a doctor be held liable? This discussion very much ties in with the final aspect of the title statement: should there be new legislation to consolidate and clarify the law on the transmission of sexual diseases?
As previously mentioned I agree on the point that it should be a punishable offence where the perpetrator was aware of his or her condition and failed to inform the victim, and to legislate based on the cases of R v Dica and R v Konzani would be no bad thing. The difficulty arises where the defendant was unsure. In order for new legislation to be clear and easily enforced, it would have to take a definite stance on the matter. Of course, this definite stance could just allow a jury to decide but that would leave the matter totally uncertain until new case law had been established.
In my opinion it seems perfectly acceptable to require those in sufficient doubt to either visit a doctor or run the risk of being reckless and thus guilty under s. 20 if they infect a sexual partner. If the test results were wrong then it would simply have to be held as an unfortunate misadventure because we clearly cannot have doctors under fear of liability for incorrect test results, and the defendant can in no way be said to have been reckless because he thought he was clean.
On a final note – my use of the word 'sufficient' doubt is unfortunately very ambiguous, but sometimes one must accept that certain points of law need to be dealt with on a case-by-case basis.
Judgments from: R v Clarence (1888) 22 QBD 23 R v Dica 3 All ER 593,  R v Konzani (2005) EWCA Crim 706 Blackstone's Statutes on Criminal Law by P. R. Glazebrook 16th Edition OUP Principles of Criminal Law by Andrew Ashworth 5th Edition OUP