(Channel 4, Cutting Edge series, broadcast on 27 March ‘08)

This documentary explores the intense connection felt between American couple Tom and Stephanie, and British couple Nick and Danielle respectively, as they face public scrutiny, and in the latter case, criminal prosecution.

Both relationships bear the common feature that each party experiences a strongly emotional and erotic attraction to their partner: each one is extraordinary in that they are siblings.

From a biological perspective, the two relationships that the programme follows are incestuous. After their mother finds them in a lovers’ embrace, half-brother and sister, Nick and Danielle, are arrested and consequently face life-imprisonment for the charge of incest. After enduring 244 days apart, the courts decide in favour of their co-habitation on the basis that they revoke any sexual relationship.

Danielle is infertile, yet a sexual relationship is illegal. In spite of the moral and ethical ramifications of Nick and Danielle’s union, the realm of thought and emotion remains closed to the law: ‘I still love her and that is not going to change for anyone’, says Nick.

Tom and Stephanie are also in love, despite the fact that they are also half brother and sister, meeting for the first time into their thirties. Similarly to Nick and Danielle, Tom and Stephanie hope for a future where their union might not bear the hallmark of incest: "I don't understand what the crime is," says Tom. "We are just two human beings in love."

The fact remains that incest avoidance (specifically interbreeding) occurs throughout the animal kingdom, and with good reason, where congenital birth defects are more likely to arise. However, if their bond is predominantly and instinctively a psychological one, the question remains whether Western society should criminalise intimate relations between couples like Nick and Danielle (who are genetically unable to bear children), or Tom and Stephanie (who choose not to).

If the union does not pose biological or genetic consequences, is any sentence fair for perpetrators of a ‘victimless’ crime?

Nick turns to the phenomenon of GSA (Genetic Sexual Attraction) to justify the extraordinary feelings he shares with his half-sister. A contributing factor to GSA is the lure of the familiar or similar.

Siblings, like all close relatives, will share some common physical and/or behavioural traits that they are likely to find attractive in a partner. These two case studies are just two of innumerable cases where children are brought up apart – often in adoptive circumstances - then meet as adults. GSA examines the complex and powerful erotic feelings that such reunions can release, and which are contrary to conventional sexual and moral structures.

Although GSA may explain these couples’ extraordinary bonds, an undercurrent of uncertainty runs through the programme: ‘In some ways it was weird...confusing’, claims Nick, but ‘it didn’t feel wrong’. GSA helps to explain that such strong feelings between siblings could belong to a delayed developmental process that brings them closer to their own identity, an identity that they may have felt disconnected from upon their early separation or as adopted children.

Around half of the reunions between siblings result in obsessive behaviour, evidenced by both examples of incest that this documentary follows, and qualified by Nick’s remark that he and Danielle ‘can’t bear to be without each other’. Similarly, Tom and Stephanie, who were both happily married for fifteen years, are prepared to "risk everything for a romantic union.

However, can this paradigm of co-dependency and exclusivity ever make up for their disownment by family and friends, or the impact on the three children that Tom leaves behind, as well as the wife that he ‘still loves’ but is no longer ‘in love’ with?

Like a higher purchase arrangement, a relationship that is unethical in principle leaves everything to chance and someone will have to forfeit their possessions (usually immaterial) or compromise their integrity. If love is not immutable, where love has a past but no tangible future, we reach an impasse. There are so many reasons why love can be wrong, where love is futile: can transgressing those boundaries ever lead to a happy union? Just because we may feel intensely erotic feelings for someone it does not always follow that we should act upon these emotions or desires.

Nick’s fierce convictions veil his underlying regret: "If I'd known about GSA before, I think forewarned is forearmed and I don't think it would have happened because I probably wouldn't have let it happen.”

As powerful and brutal as human emotion can be, as in all action engaging the emotions Love and Desire comes with responsibility. As individuals it is within our power to prevent a relationship from developing significantly, and as we belong to a collective consciousness, we have a duty to control our behaviour and resolve our emotions where desire and ethics are conflicting values. Where love is reactive, impulsive (if it is anything but), where we bend the rules of genetic and accepted moral codes, we must ultimately be prepared to face the consequences.

We live in the age of the sperm donor, in an age where jealous partners of murdered lovers are convicted of ‘crimes of passion’. The universal preoccupation with the theme of incest – and the avoidance of it (‘incest taboo’) – could be seen as a reflection of, or even a contributing factor to our deep-seated primitive fears.

The condemning of incestuous feelings and acting upon those desires, as in the case of Nick and Danielle, and Tom and Stephanie, aims to alienate the accused and in doing so will ultimately reinforce their experience of the relationship as a profoundly spiritual experience and physical bond.

By Amanda Carey/MOLI