False Prophet can sometimes tell the truth

There are several circumstances in which a False prophet can "tell the truth" ,still be liable for the death penalty, but be unable to be condemned by bais din (the court).. The reason is that he is saying something that cannot be proven to be false.

1. He quotes something that was told to another prophet and pretends that he had been told it
2. He declares that G0d told him to announce something true, but he was not commanded to announce it.
3. He declares that G0d told him to announce something, which cannot be proven true or untrue, but he was not commanded to announce it.
4. He refuses to announce something that he had been commanded to announce

An example of the first case is in Yirmiyah chapter 28, Hananiah ben Azur is called a "prophet" and not a "false prophet". The commentaries ask how a real prophet could have given a false prophecy. There are those who explain that he heard Yirmiyah giving a prophecy and that he then went elsewhere and announced it as if he had been told it himself. Others say that he heard Yirmiyah prophesy against Elam (49:35) and that he reasoned that since Elam who only helped the Chaldeans was to be punished, certainly the Babylonians themselves would be destroyed. While this could be a possible form valid logic, it was up to the prophet who had been given the prophecy (Yirmiyah) to declare this.

An example of the second case can be considered if someone declares (falsely) that G0d has commanded him to tell everyone to observe a mitzvah in the Torah (such as eating Kosher food). G0d did command us to do so and it is valid for someone to tell people to do so. However, the sin in this case is that a person is pretending to be a prophet. The last prophet (Micah) declared that there would be no further prophets until the final redemption. As a result, anyone who declared himself as a prophet during the second temple (for example) was lying. Indeed, that is how other "religions" arose after that time and why Jews have refused to accept them as valid.

An example of the third case can be found in Melachim Aleph (I Kings) chapter 13. A prophet (Iddo according to Rashi) was told to give a message to Yeravam (Jeroboam) and to return by a different road and not eat or drink along the way. As he was traveling back, an "old prophet" came to him and told him that he had been instructed by an angel that the command had been recinded and that Iddo was to come with him to eat and drink. This was a lie and Iddo was punished because he should have realized that the message would have come to him directly had it been true.

Abarbanel says that the "old prophet" thought that Iddo had given an excuse to avoid eating with Yeravam, but did not want to directly insult the king. However, Iddo should still have realized that he could not disobey his orignal command unless a malach came to him directly. When Abraham was about to sacrifice Yitzchak, he listened to the malach because the malach explained that Hashem had only wanted Yitzchak to be offered but not killed, and this had been done.

The fourth case is that of Yonah when he refused to go to Nineveh and attempted to commit suicide by going on a ship the Tarshish. He knew that he would be killed and asked the sailors to throw him overboard when he realized  that he would be condemning the innocent sailors to death with him. It was only when he had been inside the fish for three days that he realized that G0d was not going to kill him that he did teshuvah and prayed for forgiveness.

There are also cases in which bais din is required to kill the false prophet.

1. A false prophet says that the people must keep the Torah in the name of an idol
2. A flase prophet attempts to nullify a law of the Torah, even if it is in the name of G0d
3. A false prophet declares a sign and it does not come true in every detail.

An example of the first case would be if someone declared that an idol (such as y'shu) had come to him and declared that Jews should obey the laws of the Torah.

An example of the second case occured when Paul pretended to receive a "prophesy" that people were no longer required to keep kosher.

An example of the third case would be if someone tried to declare that something specific would happen at a specific date. If it happens on the wrong date, it is a false prophecy. However, if it does not happen, but it was a prophecy of punishment, and the recipient did repent, then that does not prove it a false prophesy. An example of this is Yona at Nineveh. Since Nineveh repented, the prophesy of destruction was recinded.