Catching a killer and making sure they end up behind bars is a much more lengthy and laborious process than is suggested on television police dramas like The Bill, Detective Chief Superintendent Derek Williamson said.

Before the major investigation team even arrives at the murder scene it has already been designated into groups, depending on expertise, with responsibility allocated for managing the crime scene, making house-to-house calls, making phone inquiries or liaising with the family. There will also be a team responsible for tying all the data together electronically.

Full resources are thrown into the investigation, until something sinister is either proved or disproved.

“It is a murder until you prove it is not. You can scale down rather than scale up,” said Mr Williamson.

All murder investigations are categorised depending on the level of complexity. Murders where it is not immediately obvious who was involved are classed as category A or category B. Category C murders are when it is relatively evident from the outset who the perpetrator is.

The work does not abate when a suspect is arrested. Months and even years of investigation and preparation follow to bring charges and then try to convince a jury beyond all reasonable doubt that the suspect is guilty.

During a homicide investigation an average of 2,582 documents and 572 exhibits are gathered, 536 statements taken and 1,620 actions — for example door-to-door inquiries, interviews and arrests — are taken.

Over the past 12 months the Major Investigation Teams which deal mainly with murders arrested 180 people — almost one every other day.

“When you conglomerate all those statistics together it gives some indicator of the work that goes on. Murders are very resource intensive,” said Mr Williamson.

He added: “From the murder right through to the trial you are talking about huge amounts of resources and time. The preparation required from the initial incident to a trial can be very intense. It is a much longer and more intensive process than is seen on television.”