Not sure that that is always the case.
Yes, the purpose of televised reconstructions in the UK (and in some other countries) is normally an appeal to the public for further information.
In some cases, a reconstruction may serve to genuinely establish the circumstances of in which one or more people could not have been a culprit /victim. In several cases (wherever the crimes took place), such reconstructions have been conducted by experts and not televised until trial.
And... there are others, in which the police in certain countries invite the media to witness their "success" in resolving crimes with the alleged perps, often in shackles, re-enact what they either said that they had did or what the police told them to hypothetically demonstrate.
'This is how we killed them': Chilling moment two Burmese barmen showed how they beat British pair to death on Thai beach after confessing to rape and murder following DNA match
Police lieutenant general Decha Butrnamphech said: ‘I am very satisfied with the investigation.’ Two years ago Thai police said they would stop public reconstructions of crimes using alleged perpetrators after complaints that they prejudiced trials – but they resumed after a few months. The reconstruction follows weeks of pressure on police to find the murderers of the British backpackers.
There has also been growing criticism over the standard of the investigation, from not sealing off the crime scene quickly enough to letting potential suspects leave the island.
Migrant workers, particularly from neighbouring Myanmar, have been used as scapegoats for crimes in Thailand.
A murder suspect identified only as 'Win' is brought before gathered media at today's press conference
http://www.dailymail.co.uk/news/article-2779106/Thai-police-confirm-DNA-samples-taken-Koh-Tao-murder-victims-match-two-Burmese-workers-confessed-killing-British-pair.html#ixzz4LTRZdzrQ This reenactment appears very prejudicial when one bears in mind they hadn't yet been tried for the alleged murders they were accused of having committed.
KOH TAO MURDERS - CONFESSIONS WITHDRAWN TORTURE COMPLAINTS CONFIRMEDTuesday, October 21, 2014 4
INTERPRETER WAS A PANCAKE SALESMEN WHO TOOK VICTIM'S CASH - AND NOW THAI POLICE CASE RESTS ON 'SUSPECT' DNA.Following the complete retraction of the confessions of their suspects and detailed reports of torture under interrogation assisted by a translator whose real job was selling banana and Nutella pancakes, the Royal Thai Police were left last night with uncorroborated DNA to bring to trial two migrant workers for the backpacker murders on Koh Tao.
Win Zaw Thun and Zaw Lin today emphatically denied being involved in the murders of Hannah Witheridge, 23, and David Miller, during a five hour visit, said human rights lawyer Rassada Manurassada
http://www.andrew-drummond.com/2014/10/koh-tao-murders-confessions-withdrawn.htmlThe above example and the example of the Cipriano reconstitution are not an especially auspicious advertisement for the practice which seems to be aimed at information gathering, not for the purpose of solving the case but to ease the prosecution of suspects.
Rebelo had not built any bridges with the Tapas seven or Jez Wilkins on his visit to Britain. Perhaps he and the Portuguese prosecutors should have given more consideration to the witnesses who had very real concerns for the treatment of Madeleine's parents and their own safety which first hand experience of the PJ had given them.
Some concessions and firm guarantees given could have secured their attendance ... then again, was it ever the intention to conduct a reconstitution in the first place?