In the past, vote-buying has been hard to prove because of the difficulty of obtaining evidence.

ECONOMIST: Thailand

The police decided not to mount a criminal investigation into the case earlier this year, citing the difficulty of obtaining evidence among other factors.

BBC: Two Labour peers face suspension

On Aug. 17, Dell told Wall Street it had concluded its investigation, obtaining evidence that some of the adjustments to financial statements appear to have been motivated by the desire to meet its financial targets.

FORBES: Dell Climbs Out Of Accounting Hell

Failures in the Lawrence case investigation had previously "shamed" police, he said, but they could now be commended for their work, as could the forensic scientists involved in obtaining the evidence which allowed the prosecution of Dobson and Norris to take place.

BBC: Stephen Lawrence: Gary Dobson and David Norris get life

In another twist, the same article would probably stop Italian prosecutors from obtaining the same evidence again, by making it inadmissible, in accordance with the letter of the 1959 convention.

ECONOMIST: Italy and the law

"Having regard to all the circumstances it has been concluded that, in the absence of any corroboration, the available evidence is insufficient to provide a reasonable prospect of obtaining a conviction against any individual".

BBC: No prosecution in Martin O'Hagan murder case

And even when evidence started to emerge in 2006 that the News of the World was obtaining stories in illicit ways, it took four more years for News International to identify the extent of what went wrong.

BBC: Big questions for News International