I think that in 90% of cases, recording everything helps the prosecution as much as defense. Allows them to look at nuances, catch major inconsistencies, and even help themselves know how to do better in the future.
People, including the police, don't always like change though.
If you have the equipment, doesn't make sense not to record it.
All of the 5 confessions, false confessions, of the Central Park Five were recorded. They are in Sarah Burns' documentary on the subject of the wrongful conviction of the Central Park Five. Four of the five confessions were recorded in the presence of the suspects' parent or guardian.
Very soon after, all of them recanted, claiming intimidation and coercion. Given their eventual exoneration, who doubts that even intimidation or coercion of a minor kind - with trusted family present! - can produce false confessions?
At trial there was no evidence, except for these videotapes. One of the accused said the damnable thing about the case was this - every time the defence showed that, on the evidence, he could not have participated in the crime, they would just play his confession again. They used him as a witness against himself - never acknowledging a couple of things:
1) the intimidation and coercion, even of a minor kind
2) the fact that taken together, the five stories just did not add up.
There is a reason why coercive interrogation techniques (like the Reid technique) are outlawed on the young. It is because of their high rate of producing false confessions.
This is simply a fact.
Those "confessions" actually would have helped the police and prosecutors solve the case of the Central Park jogger -
IF they saw the videos for what they were.
Proof that those five kids were actually innocent and knew nothing of the crime.
It is this that was also missed in the early morning hours of Nov 6, 2007, except this time Giuliano Mignini actually violated Italian law by not flipping the switch to record the interrogations - for Knox, for Sollecito, and for Lumumba.
Put together, their coerced stories just did not add up.
We would have seen first hand how the cops, for instance, actually prohibited Raffaele from distinguishing Wednesday night from Thursday night, on the crucial issue of Knox's whereabouts.
Raffaele has always been clear. The night of the murder, Knox was with him. Unfortunately, the cops violated the very law which Mignini quoted to Ficarra that night - and the most egregious was not taping Lumumba's interrogation.
As Lumumba said on his release, they beat the crap out of him. Beware going into interrogation when the cop says first thing, "Say, Luigi, turn off the video for a few minutes will you? We have a few things to explain to Lumumba."