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An old, but wise saying that "if it sounds too good to be true, it probably is" has been proven mathematically in a research led by University of Adelaide. A new paper to be published in Proceedings of Royal Society A, a team of researchers revealed that too much evidence without opposing opinion may weaken the credibility of a system and may even be setting itself up for failure. A case in point cited by the team of researchers is an ancient Jewish law that said a capital punishment will not be awarded to a criminal if all the judges unanimously pronounce the man guilty, reported University of Adelaide News.

"It might sound counterintuitive to say that a unanimous verdict could be wrong, but this ancient law indicated that the system may be in error if there was complete agreement among the judiciary," says corresponding author Professor Derek Abbott, a probability expert from the University of Adelaide's School of Electrical & Electronic Engineering. For the purpose of study, the team put three different scenarios to test on the basis of mathematic probability - identity of criminal verified by the eye witness; an exact validation of an archaeological item; the consistency of a cryptographic process. The researchers revealed that "too much of a goo thing" in each situation actually weakened the credibility of the result. "In our first example, we imagine there are 13 witnesses who all confidently identify a criminal suspect after seeing the suspect briefly. But getting a large group of unanimous witnesses in these circumstances is unlikely, according to the laws of probability. It's more likely the system itself is unreliable," says Professor Abbott. "In our scenario, the probability that a suspect is guilty is strong after three positive identifications by witnesses. But our tests showed that the more positive confirmations you have beyond those three, the more it erodes our confidence that this is the right person being identified.

"The situation would be quite different if the witnesses had all been taken hostage for a month by the suspect. Then you would expect them all to agree very well who the kidnapper was.

"The ancient Jewish legal practice referred to in our work indicates a surprising level of intuitive sophistication for the time, when such statistical tools would not have been at their disposal. They knew that it was rare for everyone to agree," Professor Abbott says, as reported by Science News Line