Is one who picks grapes, knowing they will be used in winemaking, considered a participant in the crimes that may occur at a wine gathering?

Most scholars have explicitly stated the prohibition of work that aids in the consumption of alcohol, such as harvesting grapes intended for pressing into wine, or transporting them, or selling them. This is based on the Almighty's saying: "{And cooperate not in sin and aggression}" (Quran 5:2), and the Prophet, peace and blessings be upon him, said: "Alcohol was cursed regarding ten [aspects]," and he mentioned among them its presser and its carrier.

Therefore, harvesting grapes for the purpose of making alcohol is not permissible. However, if this occurred before puberty, there is no sin, as the pen is lifted from the child until he reaches puberty. But if it occurred after puberty with knowledge of the prohibition, then regret, seeking forgiveness, and resolving not to return to it are sufficient.

As for you witnessing crimes due to alcohol consumption, you are not held accountable for them; this is closer to a whisper [from Shaytan].