Multiple sources indicate that a majority of ICE detainees do not have a criminal conviction, with figures around 60% lacking any criminal record, though the claim of over 70% is slightly higher than the most recent data.
Study shows over 70% of detainees held by ICE have no criminal record

FactVerify
Source: factverify.com
What the Evidence Shows
The claim states that over 70% of detainees held by ICE have no criminal record. The search results provide several data points from recent studies and internal ICE data. According to Factually.
Co, as of March 2020, more than 61% of ICE detainees had no criminal conviction, which is a majority but less than the claimed 70%. NBC San Diego reports that nearly half (47%) of detainees lack any criminal record, and fewer than 30% have been convicted of crimes, which aligns with the idea that a significant portion have no convictions but suggests a lower percentage than 70%. CBS News and other sources confirm that most detainees are not convicted violent criminals, but they do not specify that over 70% have no criminal record at all.
The data points consistently show a majority without convictions but generally around 60%, not exceeding 70%. Therefore, while the claim that most detainees have no criminal record is supported, the specific figure of over 70% appears to be an overestimate based on available data.