His blood is upon his own head/he is guilty of murder/he should bear the responsibility
Liable to death. Endangers his own life. Obligated for his own soul. An expression of warning and threat by which the responsibility for his death is placed upon him.
("And David said to him: 'Your blood is upon your own head, for your mouth has testified against you, saying, I have killed the Lord's anointed'" - 2 Samuel 1:16 (David to the man who brought him news of Saul's death and claimed he was the one who killed him), and similarly: "Our Rabbis taught: A man should not drink water neither from rivers nor from ponds at night, and if he drank, his blood is upon his own head, because of the danger" - Pesachim 112a, and also: "The householder decrees: A man who cheats in weighing, his blood is upon his own head and his nail in the cutting of his insolent eye" - Saul Tshernichovsky / Simcha Lao Davka)
Translation
Expression (Hebrew)
דָּמוֹ בְּרֹאשׁוֹ
Definition (Hebrew)
חַיָּב מִיתָה. מְסַכֵּן אֶת חַיָּיו.מִתְחַיֵּב בְּנַפְשׁוֹ. בִּטּוּי אַזְהָרָה וְאִיּוּם לְפִיו הָאַחְרָיוּת עַל מוֹתוֹ מֻנַּחַת עָלָיו.
("וַיֹּאמֶר אֵלָיו דָּוִד: דָּמְךָ עַל רֹאשֶׁךָ כִּי פִיךָ עָנָה בְךָ לֵאמֹר אָנֹכִי מֹתַתִּי אֶת מְשִׁיחַ ה'"- שְׁמוּאֵל ב א טז (דָּוִד לָאָדָם שֶׁבִּשֵּׂר לוֹ עַל מוֹת שָׁאוּל וְשֶׁטָּעַן שֶׁהוּא זֶה שֶׁהָרְגוּ), וְכֵן:"שָׁנוּ רַבּוֹתֵינוּ: לֹא יִשְׁתֶּה אָדָם מַיִם לֹא מִן הַנְּהָרוֹת וְלֹא מִן הָאֲגַמִּים בַּלַּיְלָה, וְאִם שָׁתָה דָּמוֹ בְּרֹאשׁוֹ,מִפְּנֵי הַסַּכָּנָה"- מַסֶּכֶת פְּסָחִים קיב ע"א, וְכֵן:"בַּעֲלַת הַבַּיִת גּוֹזֶרֶת:/ אִישׁ אֲשֶׁר יַחֲשֹׁד בַּהֲפָקָה, דָּמוֹ בְּרֹאשׁוֹ וְצִפָּרְנָהּ/ בְּסִירַת עֵינוֹ הַחֲצוּפָה"- שָׁאוּל טְשֶׁרְנִיחוֹבְסְקִי/ שִׂמְחָה לָאו דַּוְקָא)