Full disclosure: my first White paper looked at criminalization of HIV in the U.S. Given that I work and study in the field of public health, I am going to use this blog post to focus on some of the public health implications of criminalization, rather than the ethics or morality of criminalization itself, topics that I think other people may be better equipped to handle.
The Positive Justice Project (PJP) at the Center for HIV Law & Policy has compiled a (non-exhaustive) list of 134 prosecutions and arrests for HIV exposure in the U.S. from 2008 to the present.  The most recent case is from Florida, where a prostitute under arrest admitted to testing HIV positive; notably, the coverage of her arrest does not mention whether she was receiving anti-retroviral therapy (ART) or using condoms in her line of work.  The woman is currently facing a felony charge for failing to inform her partners of her HIV status, although one assumes since both her name and picture were published with the story, past and present johns have had ample opportunity to inform themselves.
The majority of United States HIV criminal cases involving sex also neglect to report or consider condom use and ARVs (both of which significantly reduce the risk of transmission), and spitting or biting continue to be “hazardous” behaviors worthy of arrest and felony prosecution. The Kaiser Family Foundation’s 2011 Survey of Americans on HIV/AIDS further underscores a seemingly entrenched ignorance about HIV transmission: 1 in 4 Americans believe (or do not sufficiently doubt) HIV can be transmitted via a shared drinking glass, 1 in 6 believe the same for toilet seats, and a little more than 1 in 10 view swimming pools as a potential source of infection.  In contrast, the Centers for Disease Control and Prevention (CDC) website on HIV Transmission dismisses saliva alone as a potential means of transmission, and reports that all known cases of HIV transmission via biting involved severe trauma, extensive tissue damage, and blood; bites that do not break the skin have no chance of transmitting HIV. 
A major public health concern with criminalization is that it perpetuates and reinforces myths or misperceptions of HIV risk and transmission. When an HIV-positive man or woman is charged with a felony for spitting on a police officer, despite the CDC’s official position against spitting as a feasible transmission route, it sends mixed messages about what “risky” behavior truly is, and forces the public to choose which authority they will listen to. Additionally, high profile cases fuel stigma and fear of HIV-positive people, which in turn may (although there have not yet been any studies to support this theory) inhibit testing and disclosure. Patients who fear being judged, shamed, or accused of a crime may be less willing to engage in counseling, or truthfully report sexual practices to health practitioners. 
Criminalization also shifts the responsibility for safe sex onto just one partner, a dangerous assumption given that unsafe sex can lead to any number of STIs or an unintended pregnancy, not just HIV . In other words, sex carries risks under any circumstances, not just in situations where one partner is HIV-positive. Placing the burden for safe sex entirely on the HIV-positive person’s shoulders is unjust, and can not only reinforce stigma but also cultivate complacency among HIV-negative persons. Safe sex is every person’s responsibility. Unfortunately, having just asserted the importance of equal responsibility for safe sex, it is impossible to ignore the harsh reality of gender inequality. Women are more at risk for coerced, unprotected sex in societies where they also suffer from social, economic, and political disempowerment. Women who are HIV-positive but unable to refuse sex do not deserve to be criminally prosecuted; nor do mothers who are uninformed or unsupported in attempting to prevent mother-to-child transmission.  Assuming autonomous, let alone intentional, sexual decision-making runs the risk of further victimizing already vulnerable populations.
As Judge Cameron notes, “In the majority of cases, the virus spreads when two people have consensual sex, neither of them knowing that one has HIV. That will continue to happen, no matter which criminal laws are enacted and which criminal remedies are enforced.”  The real crime in evidence here is ignorance (of status, prevention techniques, and transmission routes), which is best addressed through evidence-based public health outreach, education, and support for testing, counseling, and treatment.
 Positive Justice Project (PJP). Prosecutions and Arrests for HIV Exposure in the United States, 2008-2012. 14 Feb. 2012: http://www.hivlawandpolicy.org/resources/view/456
 Ritchie, R. Michelle Weissman busted in prostitution sting, tells deputies she’s HIV positive, police say. wptv.com, 8 Feb. 2012: http://www.wptv.com/dpp/news/region_c_palm_beach_county/lake_worth/michelle-weissman-of-lake-worth-busted-in-prostitution-sting-tells-deputies-shes-hiv-positive#ixzz1mOEu3Rwg
 Kaiser Family Foundation (KFF). HIV/AIDS at 30: A Public Opinion Perspective. June 2011: http://www.kff.org/kaiserpolls/8186.cfm
 Centers for Disease Control and Prevention (CDC). HIV/AIDS, Questions and Answers: HIV Transmission. 25 Mar. 2010: http://www.cdc.gov/hiv/resources/qa/transmission.htm
 Jürgens R, Cohen J, Cameron E, Burris S, Clayton M, Elliott R, Pearshouse R,
Gathumbi A, Cupido D. Ten reasons to oppose the criminalization of HIV exposure or transmission. Reproductive Health Matters, 2009; 17(34):163-172.
 Cameron E. Criminalization of HIV transmission: poor public health policy. HIV/AIDS Policy & Law Review, 2009; 14(2):62-75.