Much disquiet has been expressed about the anguish inflicted on the Dowler family, particularly Robert Dowler, during the recent trial of Levi Bellfield for the murder nine years ago of the Dowlers' 13-year-old daughter, Milly. It is pretty obvious that the trial handed Bellfield an opportunity to continue doing something he enjoys – inflicting extreme cruelty. Defenders of the judicial status quo say that such eventualities are regrettable, but necessary. While I also reject many of the media's emotive criticisms, I think there is currently an opportunity to consider whether the extraordinary freedom conferred on defendants in court is offered with rather too few strings attached.

Our judicial system is, of course, adversarial rather than inquisitorial. The jury hears two stories, and decides, basically, whether the prosecution's story is credible enough to withstand the alternative scenarios offered by the defence. This sounds like even-handed equality. But it is not. Prosecution witnesses must tell the truth. Anything else is perjury. Defendants can lie. Bellfield lied from the moment he offered his "not guilty" plea.

Worse, sometimes prosecution witnesses are not even allowed to tell the whole truth. I was made painfully aware of this deeply anomalous situation when I was the main prosecution witness at the trial of a burglar whom I had caught, red-handed, in my home.

The burglar had knocked on our door, and been let in by my four-year-old son, while I was feeding and settling his three-month-old brother. I knew nothing of this until I found my son sitting on the front doorstep, with the door open. He told me that he had answered the door – which at that time had clear glass panels – to "the lady in the red coat". Where was this lady now? She had gone upstairs, "to see Dad".

Grasping that there was an intruder in the house, I took the children into the living room and phoned my husband in his attic office to alert him. The phone was engaged. Realising that I was going to have to check this out myself, I started creeping towards the stairs. A hooded figure was sneaking down. I shouted, the figure started running, and I caught her as she tried to nip out of the front gate. My husband and a passerby responded to the commotion, and restrained her while I called the police.

The police charged the young woman with burglary and actual bodily harm (she'd bitten my hands, hard, to try to make me let go of her). Although there were items missing from the house, the police didn't charge her with theft. She didn't have the items on her. She had obviously been in and out already and handed them to an accomplice. This could not be proved, so the police decided it was best not to complicate matters. But that was only the first truth I was unable to tell.

I was amazed when my burglar entered a "not guilty" plea. I was even more amazed when, a few minutes before the trial began, six months after the incident, the Crown Prosecution Service told me I could not mention anything my son had said because it was hearsay evidence. That ripped my truthful narrative to shreds. Thus restricted, I was just not able to credibly explain what had happened.

The defence line was that this woman had found my son in the street and had been searching for me in the house, to deliver him to safety. As a mother herself, she had been appalled to find him wandering in the road, in danger.

But her good deed had been totally misread, and had landed her in this amazingly terrible mess. Her brief went further in her summing up. Citing the James Bulger case, she contended that people such as the defendant were afraid to intervene and save children because people such as me distorted their kind motives so grossly. People such as me, she argued, were responsible for the "walk on by" society. People such as me, she spat out contemptuously, would rather see an innocent woman go to prison than admit that they only saw the bad in people.

The trial took five days, about 20 minutes of which were taken up by the jury's deliberations. Largely, I think, because I had strongly insisted on presenting the hearsay evidence, despite the consequences and against the advice of the CPS, and the jury had believed me. After the guilty verdict had been delivered, it was revealed that this woman had 18 other burglary convictions. She regularly took advantage of children to gain entry to properties. Her own son was in care, because of her long-standing heroin addiction. She had already spent six months on remand, and was sentenced to a non-custodial drug testing and treatment regime. I was happy with that. I would have been happy with that six months before.

I am not comparing my minor ordeal to the vast suffering of the Dowler family, of course. But I do wonder if perhaps there is simply too much incentive to take a chance and plead not guilty, and too little incentive to concede guilt. Ken Clarke's ill-fated sentencing proposals recently tried to address this. Perhaps he merely got things the wrong way round. Maybe, instead of promising extra privileges for guilty pleas, we should threaten loss of privileges for failed and "mischievous" not guilty pleas. Bellfield had little to lose. Would the risk of being stripped of the special arrangements a child killer in prison receives have concentrated his mind?

Might my burglar, offered drug rehabilitation if she entered a guilty plea, and a guaranteed no-frills custodial sentence if her defence failed, have decided not to waste everyone's time, money and effort?

I am not suggesting changes in the law, or for an eroding of the rights of defendants in court. I am suggesting a change of emphasis in sentencing, whereby defendants no longer have nothing to lose from telling lies on a slender punt and absolutely everything to gain if their lies succeed. Clarke's proposed reforms invoked the carrot. Their flaw was that even a person who had no chance of being found not guilty would be further rewarded for pleading guilty. He needs to take another look at his ideas, and invert them. He needs to invoke the stick. Plead not guilty, and risk exposure as a vexatious liar, if you dare. No parole, no privileges, no quarter, just a straight, cold, maximum sentence, if you really think that you want to mess everyone around.

Surely this approach is at least worth thinking about.