Avot313

19:
Plague comes to the world because of capital crimes mandated by Torah which are not brought to court. In an environment which was ignorant of the true etiology of illness and disease it is not surprising that serious epidemics were a regular occurrence. We have here yet another example of the concept of 'measure for measure'. Those convicted of a capital crime were to be put to death by one of the four methods mandated by Torah legislation. The sages explained that the suffering of the condemned in this life would expiate their guilt so that they could inherit the life to come. Thus, goes the thinking, if the guilty were not judged the suffering must be experienced by the society that did not judge them.

20:
The problem of bringing crimes to trial was an acute one. The problem was caused by the very nature of the system. According to Torah law there was no established police force whose task it was to prevent crime and to investigate unprevented crimes and bring the perpetrator to justice. (The 'police' mandated by the Torah [Deuteronomy 16:18] are officers of the court whose task it is to see that the decisions of the judges are carried out.) Thus the task of bringing wrongdoers to justice devolved on the citizen body itself. Anyone who witnessed a crime was required by the Torah [Leviticus 5:1] to summon the culprit to court so that the judges could decide whether a crime had been committed and if so what the appropriate punishment was.

21:
In the case of capital crimes there were several problems. Firstly, the Torah requires two witnesses who simultaneously observe the crime and who warn the culprit that what he is about to do is a capital crime. (While this effectively made it very difficult – if not impossible – to apply the death sentence it would not prevent incarceration.) Thus it is the two witnesses who are the prosecution. The judges would examine them most severely. [See Sanhedrin Chapters 4 and 5, beginning at Sanhedrin 072.]

22:
Before the judges began their examination of the witnesses they would warn them of the enormous responsibility that they were taking upon themselves [Sanhedrin 4:5]:

• They must not offer testimony which is conjecture, or hearsay (even from 'a reliable source') or something told them by an original witness.
• They must be aware that their testimony will be subjected to minute examination.
• They must bear in mind that the very life of the accused is in their hands and in their testimony.

This, of course, was to warn witnesses who may be too eager to offer testimony. But the system also produced a different reaction in other would-be witnesses. Therefore the judges would also exhort the witnesses:

23:
If witnesses were reluctant to take upon themselves the burden of prosecuting testimony in capital cases – capital crimes mandated by Torah which are not brought to court – justice could not be done at all.

To be continued.

I bring forward this question from Ronen Lautman because it is topical:

You mentioned in Avot 297 that the sages didn't like the idea of supernatural miracles because they go against God's perfectly planned natural world. Is there discussion in the surrounding the story of the oil that lasted for eight days about how this apparently supernatural event was allowed to happen? Was that container of oil created 'on Friday at twilight' as well, or perhaps on Saturday evening?

I respond:

There is often a great difference between the philosophical stance taken by the sages of the Mishnah in Eretz-Israel and that taken by the sages of the Gemara in Babylon. Ĥanukah is not mentioned at all in the Mishnah (except for a passing reference). The sole source for the story of the cruse of oil is to be found in the Babylonian Talmud [Shabbat 21b-22a]. It seems most likely, from the historical point of view, that the story of the cruse of oil was included in order to introduce into the festival a measure of divine intervention to counterbalance what would otherwise have been the purely human victory of the Hasmoneans. (You can read more of this – in Hebrew – in this Dvar Torah.)