"To shed crocodile tears is to put on an insincere act of being sad." Home Affairs Correspondent Darshna Soni writes about three criminal cases which have shocked the country.
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The expression crocodile tears comes from the ancient belief that crocodiles weep while luring their prey.
In recent times, it's come to be used to describe high profile cases in which people have used the media to put on a very public display of emotion that is absolutely false.
A new documentary on Channel 4 on Thursday examines three stories that shocked the country.
On 12 May last year, I got a phone call from the newsdesk to say I should head to Derby where six children had been killed in a house fire. I remember wondering as I drove to the house what on earth their poor parents must be going through.
But three weeks later, those parents themselves, Mick and Mairead Philpott, would be charged with the murders.
It turned out that the Philpotts were well known locally. They lived an unconventional lifestyle, for years sharing their home with Mick's mistress. They had 17 children between them, and had been filmed for several reality TV shows.
"Philpott thought he was much cleverer than he really was. He'd done reality television programmes, he'd sort of taken on Jeremy Kyle," said Professor David Canter, a psychologist who studies criminal behaviour.
Crocodile tears to me could be put in the dictionary with the definition of Mick Philpott. Heather Kehoe, Philpott's ex-wife
Before they were arrested, the couple had tried to play the part of grieving parents. They had even arranged an astonishing press conference, in which they faced the world's media. I was one of the journalists who had sat watching their performance. Philpott had a lot of experience in front of the cameras so he thought he could get away with it - but it was to backfire in a spectacular way.
Speaking on camera for the first time, Philpott's ex-wife Heather Kehoe said: "It was a show that I'd seen so many times before. But it made my skin crawl to know that he could still put this act on at such a tragic time. Six children have just died and you're putting on a play.
"Crocodile tears to me could be put in the dictionary with the definition of Mick Philpott."
Tonight's documentary looks at the way in which characters like Mick Philpott try to manipulate the cameras for their own ends. We live in a media-savvy world and are all familiar with reality TV shows.
"People therefore feel confident enough to make these false appeals and express this emotion," according to Professor Canter.
The ultimate betrayal
Three months after the house fire in Derby and another case of crocodile tears. A man named Stuart Hazell in South London gives an interview to ITN in which he appears distraught about the disappearance of his 12-year-old step-granddaughter, Tia Sharp.
In the days after Tia's disappearance, Hazell had gone out searching for her with the local community, handed out leaflets and taking part in a candlit vigil. News footage shows him walking at the behind Tia's family, almost as if he was hiding at the back, trying to keep his head down.
"I think the key clue to understanding Stewart Hazell's character and the way he behaved is that he had a criminal background and was used to giving accounts of himself and getting away with it," said Professor Canter.
"He ignorantly believed he could just sort of act it out and maintain his innocence and it would all go away."
It would later emerge that Hazell had killed Tia and hidden her body upstairs in the attic. The interviews he gave were analysed and played in court.
DC Alison Grubb, a homicide detective constable, said: "As police officers we expect to be lied to. That is part of our job. But for the public, when somebody makes an appeal, they imagine that comes from the heart."
A matter of trust?
Could these cases have an effect on the public's trust? Will it mean journalists are more suspicious of family members in the future? An account of the life of Edmund Grindal, the 16th century Archbishop of Canterbury, quotes him as saying, "I begin to fear, lest his humility... be a counterfeit humility, and his tears crocodile tears."
The same day Tia Sharp was reported missing is by coincidence the same day that one of the most shocking crocodile tears cases in recent years ended. Parents, Iftikar and Farzana Ahmed, convicted for the murder of their daughter.
Shafilea was 17 years old, bright, ambitious and studying to be a lawyer. But one night in 2003, she seemed to simply vanish into the night. There was no CCTV footage of her, no forensics ever found to suggest anything untoward had happened. Her family maintained that she had run away.
Unlike the other two cases, this one went on for years. Even though the parents were arrested several times, their home bugged, their possessions searched, it seemed the police had nothing on them. During this time, I got to know the Ahmeds and their children. They invited me into their home and I interviewed them several times.
As I watched some of my old news reports, one man repeatedly featured. Milton Firman was the family's first solicitor. I met him not long after Shafilea first disappeared and remember filming him as he read a statement on the Ahmed's behalf. "They strenuously deny any involvement…"
In tonight's documentary, Mr Firman gives his first account of his relationship with the Ahmeds. Looking back, does he feel he was manipulated by their crocodile tears?
"It's not my task to make judgements about people - it's my task to do my very best to represent their interests and that's exactly what I intended to do.
"There will be those, who of course, say I was naïve, stupid, ill-advised to act on their behalf in the circumstances and to believe them.
"I would think that I was a very useful vehicle for the story that they wanted to portray. But there's nothing new about that. I mean people who commit offences will often claim to be innocent, whether they shed tears or not."
Lies, deception and betrayal. Is there a danger that cases like these will lead to increased cynicism?
"I think there is a danger that these types of cases give the impression that all appeals are false and that consequently people watching will lose confidence or faith in that and not try to help," said Prof Canter.
But we have to remember: "The great majority of police and public appeals are genuine."
Catching a killer, crocodile tears will be shown on Channel 4 on Thursday at 10pm