Another day, another uproar about sentencing. In the last two days, we've had domestic violence campaigners expressing disappointment that Justin Lee Collins received a "derisory" 140 hours of community service after being convicted of harassment, while free speech campaigners express concern that Matthew Woods has been imprisoned for 12 weeks for making "grossly offensive" jokes about missing schoolgirl April Jones.

It's never a simple case of comparing sentences like for like, as the nature of punishment will depend on several factors. However, both crimes come under the general criminal justice patchwork of protection against harassment, so why did Collins seemingly get off so lightly? Or, rather, is Woods's sentence part of what seems like a worrying obsession for punishing free speech?

A jury found Collins guilty of a single charge of harassment causing his former partner, Anna Larke, fear of violence on at least two occasions, as defined by the Protection from Harassment Act 1997. Collins seems to have been charged under section four, which says:

"A person whose course of conduct causes another to fear, on at least two occasions, that violence will be used against him is guilty of an offence if he knows or ought to know that his course of conduct will cause the other so to fear on each of those occasions."

The maximum sentence is five years. Judge John Plumstead, sentencing Collins to 140 hours unpaid work and £3,500 in prosecution costs, said it would have been to his credit had he found the courage to admit the offences. All defendants can receive up to a third off if they plead guilty at the earliest opportunity, with a smaller discount if they plead not guilty but then later change their pleas. Tom Wainwright, a criminal barrister at Garden Court chambers, said: "There is a clear incentive to reward guilty pleas in cases like this where it would avoid the need for the victim to give evidence."

So, if Collins didn't receive a discount in return for pleading, what gives?

"What may explain the lenient sentence is the nature of the charge. A lot of individual incidents have been mentioned in the reports of [Larke's] evidence but in order to convict [Collins], the jury only had to be sure of two incidents of putting the victim in fear of violence. The judge will have formed his view on the basis on which he would sentence - which may not have included the most serious allegations."

Diane Calnan, head of crime at Fisher Meredith solicitors, says: "Much depends on the pattern and persistence of the behaviour and the extent of any threats of violence." She explains that the fact that Collins avoided custody means that the judge will have considered that certain elements of the offence would not have been present, for example, deliberate threats, persistent action over a long period and an intention to cause fear of violence. "Without these elements, the sentence can range from a high level community order to 18 weeks' custody." He may have also argued that provocation was a factor.

According to Baljit Ubhey OBE, chief crown prosecutor for Thames and Chiltern CPS, there was

"clear evidence in this case that the defendant had subjected the complainant to physical, psychological and verbal abuse during the course of their relationship. A unique feature of this case is the presence of voice recordings of some of the abuse, which supported the allegation."

Then why wasn't Collins charged with assault?

A CPS spokesman said the victim's injuries did not amount to physical actual bodily harm.

"It is important to charge an offence which accurately reflects the criminality of the accused. Domestic violence often takes the form of a number of incidents which in themselves might appear relatively minor, but have a greater cumulative effect. The offence of harassment invited the jury to consider what was a course of conduct over the nine month relationship."

So, why is Woods, who posted offensive "jokes" on Facebook, facing 12 weeks in prison? Convicted under section 127 of the Communications Act 2003. The maximum penalty in this case was six months' imprisonment, Woods pleaded guilty and therefore received a discounted sentence. Although convicted under different statutes, this does not explain the disparity in sentencing, particularly bearing in mind the maximum penalties available in both cases.

Wainwright continued:

"It's difficult to comment further on [Collins's] sentence without having heard the full evidence and mitigation. I agree, it's difficult to reconcile the two cases although Woods was sentenced in the magistrates' court, where they are often perceived to be more enamoured with prison as a solution."

We know that Collins's barrister Sonia Woodley QC asked the judge to take mitigating factors into consideration and impose a financial penalty, claiming her client was on the verge of a nervous breakdown while he was with Larke. However, Plumstead said he did not think a fine "met the bill." He said: "I have not sought your means, but they are likely to be more substantial than most people ... [A community sentence] is a deprivation of your liberty and a compulsion upon you to do unpaid work for others. This will be humble work for someone who lives a prominent public life and is intended to make you pause and think about what you have done."

The aim of community sentences is to change the behaviour of the offender so they don't commit crime in the future, and to make amends to the victim of the crime or the local community. The victim in this case, Larke, welcomed the verdict. Perhaps the judge was convinced that imprisoning Collins was not appropriate, having heard evidence from his ex-wife that his behaviour was out of character.

On the face of it though, Collins escaped lightly. Meanwhile, 19-year-old Woods, will spend 12 weeks in a young offenders' institution for what his lawyer described as "one moment of drunken stupidity". His "jokes" were abhorrent, but are we moving towards an era of justice in which words are more severely punished than serial abuse?