1898 Sherman Wilcox murdered John Kosina
1920 Frank Linhart Murder
David A. Prosser convicted of the 1921 murder of Issac West, Marshal of Gas City, KS, and former Toledo, IA resident
The Iowa Unsolved Murders site has descriptions of many cases, with 6 in Tama County. Here are links to those cases:
The Czech Marble Cutter: Murder of Matej Straka 1878 Green Corn Dance Tragedy: Murder of Se-Ton-a-Qua 1897 Drinking Bout: Suspicious Death of John F. Brennan 1898 "Trio of Thugs": Murder of Officer Rolland P. Smith 1901 "The Belle of the Tribe": Murder of Ma-Sha-Che 1905 "No Women Or Children Allowed": Murder of Winfield Scott Rouse 1929