> Scalia was one of the most consistent and strong advocates for defendants' rights
That's not my impression and I quickly found the following, but I can't say the examples are representative of the overall trend or if the analyses are accurate (and I can't say the same of your examples). However, they are hard to reconcile with your claim:
1) Scalia is known for taking a hard stance against criminal defendants, and has long advocated striking down Miranda v. Arizona and upholding the constitutionality of the death penalty
http://scarinciattorney.com/supreme-court-justices/antonin-s...
2) Defendants in criminal cases have a constitutional right to a competent lawyer's advice when deciding whether to accept a plea bargain, the Supreme Court ruled ... The ruling drew a sharply worded dissent from Justice Antonin Scalia, ... He angrily called the court's rulings a "judicially invented right to effective plea bargaining." The article notes, 97% of federal convictions and 94% of state convictions result from guilty pleas.
http://articles.latimes.com/2012/mar/21/nation/la-na-court-p...
3) Ring v Arizona: holding that the Sixth Amendment requires a jury [i.e., not merely a judge] to find the aggravating factors necessary for imposing the death penalty. Scalia dissented: He voted to deny defendants the right to a jury for those purposes.
https://en.wikipedia.org/wiki/Ring_v_Arizona
4) Lawrence v Texas: The Court struck down the sodomy law in Texas and, by extension, invalidated sodomy laws in 13 other states, making same-sex sexual activity legal in every U.S. state and territory. - in 2003! Scalia dissented, which if successful (and IIUC) would have sent defendant Lawrence to prison for having sex. Again, in 2003!
https://en.wikipedia.org/wiki/Lawrence_v._Texas
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If the above is correct and I understand correctly: He opposed Miranda, the minimal requirement to inform defendants of their rights; opposed the right to an attorney for plea bargains, from which result >94% of criminal convictions; opposed the right to a jury for a essential aspect of death sentences; and voted to allow the state to imprison a defendant for having consensual sex with an adult.
I'm sure there are some grey areas, but I have a hard time seeing him as a ally of criminal defendants.